Proton control of oxidation and spin state in a series of iron tripodal imidazole complexes

Reaction of iron salts with three tripodal imidazole ligands, H(3)(1), H(3)(2), H(3)(3), formed from the condensation of tris(2-aminoethyl)amine (tren) with 3 equiv of an imidazole carboxaldehyde yielded eight new cationic iron(III) and iron(II), [FeH(3)L](3+or2+), and neutral iron(III), FeL, complexes. All complexes were characterized by EA(CHN), IR, UV, M?ssbauer, mass spectral techniques and cyclic voltammetry. Structures of three of the complexes, Fe(2).3H(2)O (C(18)H(27)FeN(10)O(3), a = b = c = 20.2707(5), cubic, I3d, Z = 16), Fe(3).4.5H(2)O (C(18)H(30)FeN(10)O(4.5), a = 20.9986(10), b = 11.7098(5), c = 19.9405(9), beta = 109.141(1), monoclinic, P2(1)/c), Z = 8), and [FeH(3)(3)](ClO(4))(2).H(2)O (C(18)H(26)Cl(2)FeN(10)O(9), a = 9.4848(4), b = 23.2354(9), c = 12.2048(5), beta = 111.147(1) degrees, monoclinic, P2(1)/n, Z = 4) were determined at 100 K. The structures are similar to one another and feature an octahedral iron with facial coordination of imidazoles and imine nitrogen atoms. The iron(III) complexes of the deprotonated ligands, Fe(1), Fe(2), and Fe(3), are low-spin while the protonated iron(III) cationic complexes, [FeH(3)(1)](ClO(4))(3) and [FeH(3)(2)](ClO(4))(3), are high-spin and spin-crossover, respectively. The iron(II) cationic complexes, [FeH(3)(1)]S(4)O(6), [FeH(3)(2)](ClO(4))(2), [FeH(3)(3)](ClO(4))(2), and [FeH(3)(3)][B(C(6)H(5))(4)](2) exhibit spin-crossover behavior. Cyclic voltammetric measurements on the series of complexes show that complete deprotonation of the ligands produces a negative shift in the Fe(III)/Fe(II) reduction potential of 981 mV on average. Deprotonation in air of either cationic iron(II) or iron(III) complexes, [FeH(3)L](3+or2+), yields the neutral iron(III) complex, FeL. The process is reversible for Fe(3), where protonation of Fe(3) yields [FeH(3)(3)](2+).     

Diverse solid-state and solution structures within a series of hexaamine dicopper(II) complexes

Mono- and dicopper(II) complexes of a series of potentially bridging hexaamine ligands have been prepared and characterized in the solid state by X-ray crystallography. The crystal structures of the following Cu(II) complexes are reported: [Cu(HL3)](ClO4)(3), C11H31Cl3CuN6O12, monoclinic, P2(1)/n, a = 8.294(2) A, b = 18.364(3) A, c = 15.674(3) A, beta = 94.73(2) degrees, Z = 4; ([Cu2(L4)(CO3)](2))(ClO4)(4).4H2O, C40H100Cl4Cu4N12O26, triclinic, P1, a = 9.4888(8) A, b = 13.353(1) A, c = 15.329(1) A, alpha = 111.250(7) degrees, beta = 90.068(8) degrees, gamma = 105.081(8) degrees, Z = 1; [Cu2(L5)(OH2)(2)](ClO4)(4), C13H36Cl4Cu2N6O18, monoclinic, P2(1)/c, a = 7.225(2) A, b = 8.5555(5) A, c = 23.134(8) A, beta = 92.37(1) degrees, Z = 2; [Cu2(L6)(OH2)(2)](ClO4)(4).3H2O, C14H44Cl4Cu2N6O21, monoclinic, P2(1)/a, a = 15.204(5) A, b = 7.6810(7) A, c = 29.370(1) A, beta = 100.42(2) degrees, Z = 4. Solution spectroscopic properties of the bimetallic complexes indicate that significant conformational changes occur upon dissolution, and this has been probed with EPR spectroscopy and molecular mechanics calculations.     

Syntheses, structures and properties of a series of non-heme alkoxide-Fe(III) complexes of a benzimidazolyl-rich ligand as models for lipoxygenase

The treatment of Fe(ClO(4))(2)·6H(2)O or Fe(ClO(4))(3)·9H(2)O with a benzimidazolyl-rich ligand, N,N,N',N'-tetrakis[(1-methyl-2-benzimidazolyl)methyl]-1,2-ethanediamine (medtb) in alcohol/MeCN gives a mononuclear ferrous complex, [Fe(II)(medtb)](ClO(4))(2)·?CH(3)CN·?CH(3)OH (1), and four non-heme alkoxide-iron(III) complexes, [Fe(III)(OMe)(medtb)](ClO(4))(2)·H(2)O (2, alcohol = MeOH), [Fe(III)(OEt)(Hmedtb)](ClO(4))(3)·CH(3)CN (3, alcohol = EtOH), [Fe(III)(O(n)Pr)(Hmedtb)](ClO(4))(3)·(n)PrOH·2CH(3)CN (4, alcohol = n-PrOH), and [Fe(III)(O(n)Bu)(Hmedtb)](ClO(4))(3)·3CH(3)CN·H(2)O (5, alcohol = n-BuOH), respectively. The alkoxide-iron(III) complexes all show 1) a Fe(III)-OR center (R = Me, 2; Et, 3; (n)Pr, 4; (n)Bu, 5) with the Fe-O bond distances in the range of 1.781-1.816 ?, and 2) a yellow color and an intense electronic transition around 370 nm. The alkoxide-iron(III) complexes can be reduced by organic compounds with a cis,cis-1,4-diene moiety via the hydrogen atom abstraction reaction.     

EPR, 1H and 2H NMR, and reactivity studies of the iron-oxygen intermediates in bioinspired catalyst systems

Complexes [(BPMEN)Fe(II)(CH(3)CN)(2)](ClO(4))(2) (1, BPMEN = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-diaminoethane) and [(TPA)Fe(II)(CH(3)CN)(2)](ClO(4))(2) (2, TPA = tris(2-pyridylmethyl)amine) are among the best nonheme iron-based catalysts for bioinspired oxidation of hydrocarbons. Using EPR and (1)H and (2)H NMR spectroscopy, the iron-oxygen intermediates formed in the catalyst systems 1,2/H(2)O(2); 1,2/H(2)O(2)/CH(3)COOH; 1,2/CH(3)CO(3)H; 1,2/m-CPBA; 1,2/PhIO; 1,2/(t)BuOOH; and 1,2/(t)BuOOH/CH(3)COOH have been studied (m-CPBA is m-chloroperbenzoic acid). The following intermediates have been observed: [(L)Fe(III)(OOR)(S)](2+), [(L)Fe(IV)═O(S)](2+) (L = BPMEN or TPA, R = H or (t)Bu, S = CH(3)CN or H(2)O), and the iron-oxygen species 1c (L = BPMEN) and 2c (L = TPA). It has been shown that 1c and 2c directly react with cyclohexene to yield cyclohexene oxide, whereas [(L)Fe(IV)═O(S)](2+) react with cyclohexene to yield mainly products of allylic oxidation. [(L)Fe(III)(OOR)(S)](2+) are inert in this reaction. The analysis of EPR and reactivity data shows that only those catalyst systems which display EPR spectra of 1c and 2c are able to selectively epoxidize cyclohexene, thus bearing strong evidence in favor of the key role of 1c and 2c in selective epoxidation. 1c and 2c were tentatively assigned to the oxoiron(V) intermediates.     

Novel iron(III) complexes of sterically hindered 4N ligands: regioselectivity in biomimetic extradiol cleavage of catechols

The iron(III) complexes of the 4N ligands 1,4-bis(2-pyridylmethyl)-1,4-diazepane (L1), 1,4-bis(6-methyl-2-pyridylmethyl)-1,4-diazepane (L2), and 1,4-bis(2-quinolylmethyl)-1,4-diazepane (L3) have been generated in situ in CH 3CN solution, characterized as [Fe(L1)Cl 2] (+) 1, [Fe(L2)Cl 2] (+) 2, and [Fe(L3)Cl 2] (+) 3 by using ESI-MS, absorption and EPR spectral and electrochemical methods and studied as functional models for the extradiol cleaving catechol dioxygenase enzymes. The tetrachlorocatecholate (TCC (2-)) adducts [Fe(L1)(TCC)](ClO 4) 1a, [Fe(L2)(TCC)](ClO 4) 2a, and [Fe(L3)(TCC)](ClO 4) 3a have been isolated and characterized by elemental analysis, absorption spectral and electrochemical methods. The molecular structure of [Fe(L1)(TCC)](ClO 4) 1a has been successfully determined by single crystal X-ray diffraction. The complex 1a possesses a distorted octahedral coordination geometry around iron(III). The two tertiary amine (Fe-N amine, 2.245, 2.145 A) and two pyridyl nitrogen (Fe-N py, 2.104, 2.249 A) atoms of the tetradentate 4N ligand are coordinated to iron(III) in a cis-beta configuration, and the two catecholate oxygen atoms of TCC (2-) occupy the remaining cis positions. The Fe-O cat bond lengths (1.940, 1.967 A) are slightly asymmetric and differ by 0.027 A only. On adding catecholate anion to all the [Fe(L)Cl 2] (+) complexes the linear tetradentate ligand rearranges itself to provide cis-coordination positions for bidentate coordination of the catechol. Upon adding 3,5-di- tert-butylcatechol (H 2DBC) pretreated with 1 equiv of Et 3N to 1- 3, only one catecholate-to-iron(III) LMCT band (648-800 nm) is observed revealing the formation of [Fe(L)(HDBC)] (2+) involving bidentate coordination of the monoanion HDBC (-). On the other hand, when H 2DBC pretreated with 2 equiv of Et 3N or 1 or 2 equiv of piperidine is added to 1- 3, two intense catecholate-to-iron(III) LMCT bands appear suggesting the formation of [Fe(L)(DBC)] (+) with bidentate coordination of DBC (2-). The appearance of the DBSQ/H 2DBC couple for [Fe(L)Cl 2] (+) at positive potentials (-0.079 to 0.165 V) upon treatment with DBC (2-) reveals that chelated DBC (2-) in the former is stabilized toward oxidation more than the uncoordinated H 2DBC. It is remarkable that the [Fe(L)(HDBC)] (2+) complexes elicit fast regioselective extradiol cleavage (34.6-85.5%) in the presence of O 2 unlike the iron(III) complexes of the analogous linear 4N ligands known so far to yield intradiol cleavage products exclusively. Also, the adduct [Fe(L2)(HDBC)] (2+) shows a higher extradiol to intradiol cleavage product selectivity ( E/ I, 181:1) than the other adducts [Fe(L3)(HDBC)] (2+) ( E/ I, 57:1) and [Fe(L1)(HDBC)] (2+) ( E/ I, 9:1). It is proposed that the coordinated pyridyl nitrogen abstracts the proton from chelated HDBC (-) in the substrate-bound complex and then gets displaced to facilitate O 2 attack on the iron(III) center to yield the extradiol cleavage product. In contrast, when the cleavage reaction is performed in the presence of a stronger base like piperidine or 2 equiv of Et 3N a faster intradiol cleavage is favored over extradiol cleavage suggesting the importance of bidentate coordination of DBC (2-) in facilitating intradiol cleavage.     

Redox-noninnocence of the S,S'-coordinated ligands in bis(benzene-1,2-dithiolato)iron complexes

The electronic structures of complexes of iron containing two S,S'-coordinated benzene-1,2-dithiolate, (L)(2)(-), or 3,5-di-tert-butyl-1,2-benzenedithiolate, (L(Bu))(2)(-), ligands have been elucidated in depth by electronic absorption, infrared, X-band EPR, and Mossbauer spectroscopies. It is conclusively shown that, in contrast to earlier reports, high-valent iron(IV) (d(4), S = 1) is not accessible in this chemistry. Instead, the S,S'-coordinated radical monoanions (L(*))(1)(-) and/or (L(Bu)(*))(1)(-) prevail. Thus, five-coordinate [Fe(L)(2)(PMe(3))] has an electronic structure which is best described as [Fe(III)(L)(L(*))(PMe(3))] where the observed triplet ground state of the molecule is attained via intramolecular, strong antiferromagnetic spin coupling between an intermediate spin ferric ion (S(Fe) = (3)/(2)) and a ligand radical (L(*))(1)(-) (S(rad) = (1)/(2)). The following complexes containing only benzene-1,2-dithiolate(2-) ligands have been synthesized, and their electronic structures have been studied in detail: [NH(C(2)H(5))(3)](2)[Fe(II)(L)(2)] (1), [N(n-Bu)(4)](2)[Fe(III)(2)(L)(4)] (2), [N(n-Bu)(4)](2)[Fe(III)(2)(L(Bu))(4)] (3); [P(CH(3))Ph(3)][Fe(III)(L)(2)(t-Bu-py)] (4) where t-Bu-py is 4-tert-butylpyridine. Complexes containing an Fe(III)(L(*))(L)- or Fe(III)(L(Bu))(L(Bu)(*))- moiety are [N(n-Bu)(4)][Fe(III)(2)(L(Bu))(3)(L(Bu)(*))] (3(ox)()), [Fe(III)(L)(L(*))(t-Bu-py)] (4(ox)()), [Fe(III)(L(Bu))(L(Bu)(*))(PMe(3))] (7), [Fe(III)(L(Bu))(L(Bu)(*))(PMe(3))(2)] (8), and [Fe(III)(L(Bu))(L(Bu)(*))(PPr(3))] (9), where Pr represents the n-propyl substituent. Complexes 2, 3(ox)(), 4, [Fe(III)(L)(L(*))(PMe(3))(2)] (6), and 9 have been structurally characterized by X-ray crystallography.     

Syntheses and structural characterization of dinuclear and tetranuclear iron(III) complexes with dinucleating ligands and their reactions with hydrogen peroxide

The iron(III) complexes [Fe(2)(HPTB)(mu-OH)(NO(3))(2)](NO(3))(2).CH(3)OH.2H(2)O (1), [Fe(2)(HPTB)(mu-OCH(3))(NO(3))(2)](NO(3))(2).4.5CH(3)OH (2), [Fe(2)(HPTB)(mu-OH)(OBz)(2)](ClO(4))(2).4.5H(2)O (3), [Fe(2)(N-EtOH-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3CH(3)OH.1.5H(2)O (4), [Fe(2)(5,6-Me(2)-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3.5CH(3)OH.C(2)H(5)OC(2)H(5).0.5H(2)O (5), and [Fe(4)(HPTB)(2)(mu-F)(2)(OH)(4)](ClO(4))(4).CH(3)CN.C(2)H(5)OC(2)H(5).H(2)O (6) were synthesized (HPTB = N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, N-EtOH-HPTB = N,N,N',N'-tetrakis(N' '-(2-hydroxoethyl)-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, 5,6-Me(2)-HPTB = N,N,N',N'-tetrakis(5,6-dimethyl-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane). The molecular structures of 2-6 were established by single-crystal X-ray crystallography. Iron(II) complexes with ligands similar to the dinucleating ligands described herein have been used previously as model compounds for the dioxygen uptake at the active sites of non-heme iron enzymes. The same metastable (mu-peroxo)diiron(III) adducts were observed during these studies. They can be prepared by adding hydrogen peroxide to the iron(III) compounds 1-6. Using stopped-flow techniques these reactions were kinetically investigated in different solvents and a mechanism was postulated.     

Syntheses, structures, and reactivity of low spin iron(III) complexes containing a single carboxamido nitrogen in a [FeN5L] chromophore

A new pentacoordinate ligand based on TPA (tris-(2-pyridylmethyl)amine), namely, N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide (PaPy(3)H), has been synthesized. The iron(III) complexes of this ligand, namely, [Fe(PaPy(3))(CH(3)CN)](ClO(4))(2) (1), [Fe(PaPy(3))(Cl)]ClO(4) (2), [Fe(PaPy(3))(CN)]ClO(4) (3), and [Fe(PaPy(3))(N(3))]ClO(4) (4), have been isolated and complexes 1-3 have been structurally characterized. These complexes are the first examples of monomeric iron(III) complexes with one carboxamido nitrogen in the first coordination sphere. All four complexes are low spin and exhibit rhombic EPR signals around g = 2. The solvent bound species [Fe(PaPy(3))(CH(3)CN)](ClO(4))(2) reacts with H(2)O(2) in acetonitrile at low temperature to afford [Fe(PaPy(3))(OOH)](+) (g = 2.24, 2.14, 1.96). When cyclohexene is allowed to react with 1/H(2)O(2) at room temperature, a significant amount of cyclohexene oxide is produced along with the allylic oxidation products. Analysis of the oxidation products indicates that the allylic oxidation products arise from a radical-driven autoxidation process while the epoxidation is carried out by a distinctly different oxidant. No epoxidation of cyclohexene is observed with 1/TBHP.     

Nitrosyliron(III) porphyrinates: porphyrin core conformation and FeNO geometry. Any correlation?

The synthesis, structural, and spectroscopic characterization of (nitrosyl)iron(III) porphyrinate complexes designed to have strongly nonplanar porphyrin core conformations is reported. The species have a nitrogen-donor axial ligand trans to the nitrosyl ligand and display planar as well as highly nonplanar porphyrin core conformations. The systems were designed to test the idea, expressly discussed for the heme protein nitrophorin (Roberts, et al. Biochemistry 2001, 40, 11327), that porphyrin core distortions could lead to an unexpected, bent geometry for the FeNO group. For [Fe(OETPP)(1-MeIm)(NO)]ClO(4).C(6)H(5)Cl (H(2)OETPP = octaethyltetraphenylporphyrin), the porphyrin core is found to be severely saddled. However, this distortion has little or no effect on the geometric parameters of the coordination group: Fe-N(p) = 1.990(9) A, Fe-N(NO) = 1.650(2) A, Fe-N(L) = 1.983(2) A, and Fe-N-O = 177.0(3) degrees. For the complex [Fe(OEP)(2-MeHIm)(NO)]ClO(4).0.5CH(2)Cl(2) (H(2)OEP = octaethylporphyrin), there are two independent molecules in the asymmetric unit. The cation denoted [Fe(OEP)(2-MeHIm)(NO)](+)(pla) has a close-to-planar porphyrin core. For this cation, Fe-N(p) = 2.014(8) A, Fe-N(NO) = 1.649(2) A, Fe-N(L) = 2.053(2) A, and Fe-N-O = 175.6(2) degrees. The second cation, [Fe(OEP)(2-MeHIm)(NO)](+)(ruf), has a ruffled core: Fe-N(p) = 2.003(7) A, Fe-N(NO) = 1.648(2) A, Fe-N(L) = 2.032(2) A, and Fe-N-O = 177.4(2) degrees. Thus, there is no effect on the coordination group geometry caused by either type of nonplanar core deformation; it is unlikely that a protein engendered core deformation would cause FeNO bending either. The solid-state nitrosyl stretching frequencies of 1917 cm(-)(1) for [Fe(OEP)(2-MeHIm)(NO)]ClO(4) and 1871 cm(-)(1) for [Fe(OETPP)(1-MeIm)(NO)]ClO(4) are well within the range seen for linear Fe-N-O groups. M?ssbauer data for [Fe(OEP)(2-MeHIm)(NO)]ClO(4) confirm that the ground state is diamagnetic. In addition, the quadrupole splitting value of 1.88 mm/s and isomer shift (0.05 mm/s) at 4.2 K are similar to other (nitrosyl)iron(III) porphyrin complexes with linear Fe-N-O groups. Crystal data: [Fe(OETPP)(1-MeIm)(NO)]ClO(4).C(6)H(5)Cl, monoclinic, space group P2(1)/c, Z = 4, with a = 12.9829(6) A, b = 36.305(2) A, c = 14.0126(6) A, beta = 108.087(1) degrees; [Fe(OEP)(2-MeHIm)(NO)]ClO(4).0.5CH(2)Cl(2), triclinic, space group Ponemacr;, Z = 4, with a = 14.062(2) A, b = 16.175(3) A, c = 19.948(3) A, alpha = 69.427(3) degrees, beta = 71.504(3) degrees, gamma = 89.054(3) degrees.     

Self-assembled supramolecular M9 (Mn(II), Fe(III), Zn(II)), M5 (Fe(III)), and [M3]2 (Pb(II)) complexes: structural,magnetic, and Mössbauer properties

The tritopic ligand 2poap self-assembles in the presence of Zn(NO(3))(2) and Fe(NO(3))(3) to form homoleptic [3 x 3] nonanuclear M(9) (M = Zn(II), Fe(III)) square grid structures and with Pb(ClO(4))(2) to form a dimerized linear trinuclear [Pb(3)](2) structure. Cl2poap and Cl2poapz form self-assembled homoleptic [3 x 3] Mn(II)(9) square grids with Mn(ClO(4))(2) and Mn(NO(3))(2), respectively, but an unusual incompletely metalated Fe(III)(5) square grid is formed on reaction of Cl2poap with Fe(ClO(4))(3). X-ray structures are reported for [Mn(9)(Cl2poap-2H)(6)](ClO(4))(6).10H(2)O (3), [Mn(9)(Cl2poapz-2H)(6)] (NO(3))(6).22H(2)O (4), [Zn(9)(2poap-2H)(3)(2poap-H)(3)](NO(3))(9).24H(2)O (5), [Pb(3)(2poap-2H) (ClO(4))(4)](2).8H(2)O (6), and [Fe(5)(Cl2poap-H)(6)](ClO(4))(9).34.5H(2)O (7). Compound 3 crystallized in the monoclinic system, space group P(-)1, with a = 18.179(1) A, b = 18.857(1) A, c = 25.871(2) A, alpha = 70.506(2) degrees, beta = 86.440(1) degrees, gamma = 75.175(2) degrees, and z = 2. Compound 4 crystallized in the monoclinic system, space group P(-)1, with a = 16.900(2) A, b = 20.02393) A, c = 25.663() A, alpha = 84.743(3) degrees, beta = 84.885(2) degrees, gamma = 67.081(2) degrees, and z = 2. Compound 5 crystallized in the monoclinic system, space group P(-)1, with a = 18.482(1) A, b = 18.774(1) A, c = 28.112(2) A, alpha = 104.020(1) degrees, beta = 97.791(1) degrees, gamma = 117.036(1) degrees, and z = 2. Compound 6 crystallized in the monoclinic system, space group P(-)1, with a = 10.0513(6) A, b = 11.0958(6) A, c = 17.334(1) A, alpha = 100.932(1) degrees, beta = 100.387(1) degrees, gamma = 94.565(1) degrees, and z = 2. Compound 7 crystallized in the monoclinic system, space group P(-)1, with a = 19.164(1) A, b = 19.587(2) A, c = 26.673(2) A, alpha = 76.430(2) degrees, beta = 78.834(2) degrees, gamma = 64.973(1) degrees, and z = 2. Compound 3 exhibits intramolecular antiferromagnetic exchange within the nonanuclear [Mn(9)(mu-O)(12)] grid structure (J = -4.6 cm(-1)), while the analogous nonanuclear complex [Fe(9)(2poap-2H)(6)](NO(3))(15).18H(2)O (8) is dominated by intramolecular antiferromagnetic coupling at high temperatures but exhibits a low-temperature feature indicative of additional ferromagnetic interactions. The isolated pentanuclear Fe(5) [4 + 1] square grid in 7, with distant Fe-Fe bridging, exhibits very weak antiferromagnetic coupling (J = -0.2 cm(-1)). M?ssbauer spectroscopy data are consistent with high-spin Fe(III)(9) and Fe(III)(5) structures.     

Reactivity of a (mu-oxo)(mu-hydroxo)diiron(III) diamond core with water, urea, substituted ureas, and acetamide

A series of iron(III) complexes of the tetradentate ligand BPMEN (N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine) were prepared and structurally characterized. Complex [Fe(2)(mu-O)(mu-OH)(BPMEN)(2)](ClO(4))(3) (1) contains a (mu-oxo)(mu-hydroxo)diiron(III) diamond core. Complex [Fe(BPMEN)(urea)(OEt)](ClO(4))(2) (2) is a rare example of a mononuclear non-heme iron(III) alkoxide complex. Complexes [Fe(2)(mu-O)(mu-OC(NH(2))NH)(BPMEN)(2)](ClO(4))(3) (3) and [Fe(2)(mu-O)(mu-OC(NHMe)NH)(BPMEN)(2)](ClO(4))(3) (4) feature N,O-bridging deprotonated urea ligands. The kinetics and equilibrium of the reactions of 1 with ligands L (L = water, urea, 1-methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, and acetamide) in acetonitrile solutions were studied by stopped-flow UV-vis spectrophotometry, NMR, and mass spectrometry. All these ligands react with 1 in a rapid equilibrium, opening the four-membered Fe(III)(mu-O)(mu-OH)Fe(III) core and forming intermediates with a (HO)Fe(III)(mu-O)Fe(III)(L) core. The entropy and enthalpy for urea binding through oxygen are DeltaH degrees = -25 kJ mol(-1) and DeltaS degrees = -53.4 J mol(-1) K(-1) with an equilibrium constant of K(1) = 37 L mol(-1) at 25 degrees C. Addition of methyl groups on one of the urea nitrogen did not affect this reaction, but the addition of methyl groups on both nitrogens considerably decreased the value of K(1). An opening of the hydroxo bridge in the diamond core complex [Fe(2)(mu-O)(mu-OH)(BPMEN)(2)] is a rapid associative process, with activation enthalpy of about 60 kJ mol(-1) and activation entropies ranging from -25 to -43 J mol(-1) K(-1). For the incoming ligands with the -CONH(2) functionality (urea, 1-methylurea, 1,1-dimethylurea, and acetamide), a second, slow step occurs, leading to the formation of stable N,O-coordinated amidate diiron(III) species such as 3 and 4. The rate of this ring-closure reaction is controlled by the steric bulk of the incoming ligand and by the acidity of the amide group.     

Preparation of highly efficient manganese catalase mimics

The series of compounds [Mn(bpia)(mu-OAc)](2)(ClO(4))(2) (1), [Mn(2)(bpia)(2)(muO)(mu-OAc)](ClO(4))(3).CH(3)CN (2), [Mn(bpia)(mu-O)](2)(ClO(4))(2)(PF(6)).2CH(3)CN (3), [Mn(bpia)(Cl)(2)](ClO)(4) (4), and [(Mn(bpia)(Cl))(2)(mu-O)](ClO(4))(2).2CH(3)CN (5) (bpia = bis(picolyl)(N-methylimidazol-2-yl)amine) represents a structural, spectroscopic, and functional model system for manganese catalases. Compounds 3 and 5 have been synthesized from 2 via bulk electrolysis and ligand exchange, respectively. All complexes have been structurally characterized by X-ray crystallography and by UV-vis and EPR spectroscopies. The different bridging ligands including the rare mono-mu-oxo and mono-mu-oxo-mono-mu-carboxylato motifs lead to a variation of the Mn-Mn separation across the four binuclear compounds of 1.50 A (Mn(2)(II,II) = 4.128 A, Mn(2)(III,III) = 3.5326 and 3.2533 A, Mn(2)(III,IV) = 2.624 A). Complexes 1, 2, and 3 are mimics for the Mn(2)(II,II), the Mn(2)(III,III), and the Mn(2)(III,IV) oxidation states of the native enzyme. UV-vis spectra of these compounds show similarities to those of the corresponding oxidation states of manganese catalase from Thermus thermophilus and Lactobacillus plantarum. Compound 2 exhibits a rare example of a Jahn-Teller compression. While complexes 1 and 3 are efficient catalysts for the disproportionation of hydrogen peroxide and contain an N(4)O(2) donor set, 4 and 5 show no catalase activity. These complexes have an N(4)Cl(2) and N(4)OCl donor set, respectively, and serve as mimics for halide inhibited manganese catalases. Cyclovoltammetric data show that the substitution of oxygen donor atoms with chloride causes a shift of redox potentials to more positive values. To our knowledge, complex 1 is the most efficient binuclear functional manganese catalase mimic exhibiting saturation kinetics to date.     

Synthesis, Characterization, and Crystal Structure of a (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Hexapyridine Ligand, 1,2-Bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane. The First Example of a Discrete (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Ligand

A mononucleating tripyridine ligand, 2-(bis(2-pyridyl)methyl)-6-methylpyridine (L(1)), and a dinucleating hexapyridine ligand, 1,2-bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane (L(2)), have been prepared. The reaction of a carbanion of 2,6-lutidine with 2-bromopyridine affords L(1) which is converted to L(2) quantitatively by treating with tert-butyllithium and 1,2-dibromoethane. (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) complexes [Fe(2)(O)(OAc)(2)(L(1))(2)](ClO(4))(2) (1) and [Fe(2)(O)(OAc)(2)L(2)](ClO(4))(2) (2) have been synthesized and characterized by means of infrared, UV/vis, mass, and M?ssbauer spectroscopies and by measuring magnetic susceptibility and cyclic voltammograms. All the spectral data are consistent with the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure in both 1 and 2. A relatively strong molecular ion peak at m/z 865 corresponding to [{Fe(2)O(OAc)(2)L(2)}(ClO(4))](+) in a FAB mass spectrum of 2 suggests the stabilization of the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure by L(2) in a solution state. The compound 2.DMF.2-PrOH.H(2)O, chemical formula C(44)Cl(2)Fe(2)H(51)N(7)O(16), crystallizes in the monoclinic space group C2/c with a = 22.034(6) ?, b = 12.595(5) ?, c = 20.651(7) ?, beta = 121.49(2) degrees, and Z = 4. The cation has 2-fold symmetry with the bridging oxygen atom on the 2-fold axis: Fe-(&mgr;-O) = 1.782(5) ?, Fe-O-Fe = 123.6(6) degrees, and Fe.Fe = 3.142(3) ?. The diiron(III) core structure of 2 seems to be stabilized by encapsulation of the ligand. Compound 2 is the first example of a discrete (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) complex with a dinucleating ligand.     

Influence of bulky N-substituents on the formation of lanthanide triple helical complexes with a ligand derived from bis(benzimidazole)pyridine: structural and thermodynamic evidence

The planar aromatic tridentate ligand 2,6-bis(1-S-neopentylbenzimidazol-2-yl)pyridine (L(11)) reacts with Ln(III) (Ln = La-Lu) in acetonitrile to give the successive complexes [Ln(L(11))(n)](3+) (n = 1-3). However, stability constants determined by spectrophotometry and NMR titrations show that formation of the tris complexes is not favored, log K(3) being around 1 for La(III) and Eu(III), while no such species could be evidenced for the smaller Lu(III) ion. The X-ray structures of L(11) (monoclinic, P2(1), a = 13.4850(12) A, b = 12.0243(11) A, c = 16.4239(14) A, beta = 103.747(7) degrees ), [La(ClO(4))(2)(L(11))(2)](3)[La(ClO(4))(2)(H(2)O)(L(11))(2)](ClO(4))(4).15MeCN (1a, monoclinic, P2(1), a = 21.765(4) A, b = 30.769(6) A, c = 21.541(5) A, beta = 116.01(3) degrees ), and [Eu(L(11))(3)](ClO(4))(3).4.28MeCN (5a, monoclinic, P1, a = 14.166(3) A, b = 19.212(4) A, c = 21.099(4) A, alpha = 108.91(3) degrees, beta = 98.22(3) degrees, gamma = 108.40(3) degrees ) have been solved. In 1a, two different types of complex cations are evidenced, both containing 10-coordinate La(III) ions. In the first type, both perchlorate anions are bidentate, while in the second type, one perchlorate is monodentate, the 10th coordination position being occupied by a water molecule. In 5a the three ligands are not equivalent. Ligands A and B are wrapped in a helical way and are mirror images of each other, while ligand C lies almost perpendicular to the two other ones. This stems from the steric hindrance generated by the bulky neopentyl groups with the consecutive loss of any stabilizing interstrand pi-stacking interactions. This explains the low stability of the tris complexes and the difficulty of isolating them and points to the importance of the steric factors in the design of self-assembled triple helical lanthanide-containing functional edifices [Ln(L(i))(3)](3+).     

N,N,N ',N '-Tetrakis(2-pyridylmethyl)ethylenediamine and its analogues as hypodentate ligands. Synthesis and characterization of the rhodium(III), ruthenium(II), and palladium(II) complexes

New complexes of Rh(III), Ru(II), and Pd(II) with N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (tpen) and its analogues have been prepared. The reaction of RhCl(3).nH(2)O with tpen is slow and allows one to isolate the products of three consecutive substitution steps: Rh(2)Cl(6)(tpen) (1), cis-[RhCl(2)(eta(4)-tpen)](+) (2), and [RhCl(eta(5)-tpen)](2+) (3). In acetonitrile the reaction stops at the step of the formation of cis-[RhCl(2)(eta(4)-tpen)](+), whereas [RhCl(eta(5)-tpen)](2+) is the final product of the further reaction in ethanol. Fully chelated [Rh(tpen)](3+) could not be obtained. Bis(acetylacetonato)palladium(II), Pd(acac)(2), reacts with tpen and its analogues, N,N,N',N'-tetrakis(2-pyridylmethyl)-1,3-propanediamine (tptn) and N,N,N',N'-tetrakis(2-pyridylmethyl)-(R)-1,2-propylenediamine (R-tppn), to give [Pd(eta(4)-tpen)](2+) (4), [Pd(eta(4)-tppn)](2+) (5), and [Pd(eta(4)-tptn)](2+) (6), respectively. Two pyridyl arms remain uncoordinated in these cases. The formation of unstable Pd(III) complexes from these Pd(II) complexes in solution was suggested on the basis of electrochemical measurements. Ruthenium(III) trichloride, RuCl(3).nH(2)O, is reduced to give a Ru(II) complex with fully coordinated tpen, [Ru(tpen)](2+) (7). The same product was obtained in a more straightforward reaction of Ru(II)Cl(2)(dimethyl sulfoxide)(4) with tpen. Electrochemical studies showed a quasi-reversible [Ru(tpen)](2+/3+) couple for [7](ClO(4))(2) (E(1/2) = 1.05 V vs Ag/AgCl). Crystal structures of [2](PF(6)).2CH(3)CN, [3](PF(6))(2).CH(3)CN, [6](ClO(4))(2), and [7](ClO(4))(2).0.5H(2)O were determined. Crystal data: [2](PF(6)).2CH(3)CN, monoclinic, C2, a = 16.974(4) A, b = 8.064(3) A, c = 13.247(3) A, beta = 106.37(2) degrees, V = 1739.9(8) A(3), Z = 2; [3](PF(6))(2).CH(3)CN, triclinic, P1, a = 11.430(1) A, b = 19.234(3) A, c = 8.101(1) A, alpha = 99.43(1) degrees, beta = 93.89(1) degrees, gamma = 80.10(1) degrees, V = 1729.3(4) A(3), Z = 2; [6](ClO(4))(2), orthorhombic, Pnna, a = 8.147(1) A, b = 25.57(1) A, c = 14.770(4) A, V = 3076(3) A(3), Z = 4; [7](ClO(4))(2).0.5H(2)O, monoclinic, P2(1)/c, a = 10.046(7) A, b = 19.049(2) A, c = 15.696(3) A, beta = 101.46(3) degrees, V = 2943(2) A(3), Z = 4.     

On the reactivity toward ketones of new methyl amino complexes of Rh(III) and Ag(I). Synthesis of ortho-rhodiated acetophenone methyl imine complexes

MeNH(2) reacts with silver salts AgX (2:1) to give [Ag(NH(2)Me)(2)]X [X = TfO = CF(3)SO(3) (1.TfO) and ClO(4) (1.ClO(4))]. Neutral mono(amino) Rh(III) complexes [Rh(Cp*)Cl(2)(NH(2)R)] [R = Me (2a), To = C(6)H(4)Me-4 (2b)] have been prepared by reacting [Rh(Cp*)Cl(mu-Cl)](2) with RNH(2) (1:2). The following cationic methyl amino complexes have also been prepared: [Rh(Cp*)Cl(NH(2)Me)(PPh(3))]TfO (3.TfO), from [Rh(Cp*)Cl(2)(PPh(3))] and 1.TfO (1:1); [Rh(Cp*)Cl(NH(2)R)2]X, where R = Me, X = Cl, (4a.Cl), from [Rh(Cp*)Cl(mu-Cl)]2 and MeNH2 (1:4), or R = Me, X = ClO4 (4a.ClO4), from 4a.Cl and NaClO4 (1:4.8), or R = To, X = TfO (4b.TfO), from [Rh(Cp*)Cl(mu-Cl)](2), ToNH(2) and TlTfO (1:4:2); [Rh(Cp*)(NH(2)Me)(tBubpy)](TfO)(2) (tBubpy = 4,4'-di-tert-butyl-2,2'-bipyridine, 5.TfO), from 2a, TlTfO and tBubpy (1:2:1); [Rh(Cp*)(NH(2)Me)(3)](TfO)2 (6.TfO) from [Rh(Cp*)Cl(mu-Cl)](2) and 1.TfO (1:4). 2-6 constitute the first family of methyl amino complexes of rhodium. 1 and 4a.ClO(4) react with acetone to give, respectively, the methyl imino complexes [Ag{N(Me)=CMe(2)}()]X [X = TfO (7.TfO), ClO(4) (7.ClO(4))], and [Rh(Cp*)Cl(Me-imam)]ClO(4) [8.ClO(4), Me-imam = N,N'-N(Me)=C(Me)CH(2)C(Me)(2)NHMe]. 7.X (X = TfO, ClO(4)) are new members of the small family of methyl acetimino complexes of any metal whereas 8.ClO4 results after a double acetone condensation to give the corresponding bis(methyl acetimino) complex and an aldol-like condensation of the two imino ligands. The acetimino complex [Ag(NH=CMe(2))(2)]ClO(4) reacts with [Rh(Cp*)Cl(imam)]ClO(4) [1:1, imam = N,N'-NH=C(Me)CH(2)C(Me)(2)NH(2)] to give [Rh(Cp*)(imam)(NH=CMe(2))](ClO(4))(2) (9a.ClO(4)). 8.ClO(4) reacts with AgClO(4) (1:1) in MeCN to give [Rh(Cp*)(Me-imam)(NCMe)](ClO(4))2 (9b.ClO(4)), which in turn reacts with XyNC (Xy = C(6)H(3)Me(2)-2,6) or with MeNH(2) (1:1) to give [Rh(Cp*)(Me-imam)L](ClO(4))(2) [L = XyNC (9c.ClO(4)), MeNH(2) (9d.ClO(4))]. 6.TfO reacts with acetophenone to give [Rh(Cp*){C,N-C(6)H(4)C(Me)=N(Me)-2}(NH(2)Me)]TfO (10a.TfO), the first complex resulting from such a condensation and cyclometalation reaction. In turn, 10a.TfO reacts with isocyanides RNC (1:1) at room temperature to give [Rh(Cp*){C,N-C(6)H(4)C(Me)=NMe-2}(CNR)]TfO [R = tBu (10b.TfO), Xy (10c.TfO)], or 1:12 at 60 degrees C to give [Rh(Cp*){C,N-C(=NXy)C(6)H(4)C(Me)=N(Me)-2}(CNXy)]TfO (11.TfO). The crystal structures of 9a.ClO(4).acetone-d6, 9c.ClO(4), and 10a.TfO have been determined.     

Acid-base equilibrium of aqua-chromium-dioxolene complexes aimed at formation of oxo-chromium complexes

A series of aqua-Cr(III)-dioxolene complexes, [Cr(OH(2))(3,5-Bu(2)SQ)(trpy)](ClO(4))(2) (1s), [Cr(OH(2))(3,5-Bu(2)Cat)(trpy)]ClO(4) (1c), [Cr(OH(2))(3,6-Bu(2)SQ)(trpy)](ClO(4))(2) (2), [Cr(OH(2))(Cat)(trpy)]ClO(4) (3), [Cr(OH(2))(Cl(4)Cat)(trpy)]ClO(4) (4), [Cr(OH(2))(3,5-Bu(2)SQ)(Me(3)-tacn)](ClO(4))(2) (5), [Cr(OH(2))(Cat)(Me(3)-tacn)]ClO(4) (6), and [Cr(OH(2))(Cl(4)Cat)(Me(3)-tacn)]ClO(4) (7) (Bu(2)SQ = di-tert-butyl-o-benzosemiquinonate anion, Bu(2)Cat = di-tert-butylcatecholate dianion, Cat = catecholate dianion, Cl(4)Cat = tetrachlorocatecholate dianion, trpy = 2,2':6',2' '-terpyridine, and Me(3)-tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane), were prepared. On the basis of the crystal structures, redox behavior, and elemental analyses of these complexes, dioxolene in 1c, 3, 4, 6, and 7 coordinated to Cr(III) as the catechol form, and the ligand in 1s, 2, and 5 was linked to Cr(III) with the semiquinone form. All the aqua-Cr(III) complexes reversibly changed to the hydroxo-Cr(III) ones upon dissociation of the aqua proton, and the pK(a) value of the aqua-Cr(III) complexes increased in the order 6 > 3 approximately 1c > 7 > 5 approximately 4 > 1s. Hydroxo-Cr(III)-catechol complexes derived from 1c, 3, 4, 6, and 7 did not show any signs of dissociation of their hydroxy proton. On the other hand, hydroxo-Cr(III)-semiquinone complexes were reduced to hydroxo-Cr(III)-catechol in H(2)O/THF at pH 11 under illumination of visible light.     

Synthesis and Characterization of Six-Coordinate Nitrido Complexes of Vanadium(V), Chromium(V), and Manganese(V). Isolation of a Dinuclear, Mixed-Valent &mgr;-Nitrido Chromium(III)/Chromium(V) Species

Photolysis of a series of octahedral monoazido complexes of the type [LM(III)(didentate ligand)(N(3))](n)(+)X(n) of vanadium(III), chromium(III), and manganese(III) in the solid state or in solution yields quantitatively the corresponding six-coordinate nitrido complexes [LM(V)(didentate ligand)(N)](n)(+)X(n) and 1 equiv of dinitrogen. L represents the macrocycle 1,4,7-triazacyclononane or its N-methylated derivative (L'), the didentate ligands are pentane-2,4-dionate (acac), 2,2,6,6-tetramethylheptane-3,5-dionate (tacac), picolinate (pic), phenanthroline (phen), and oxalate (ox), and X(-) represents perchlorate or hexafluorophosphate. The following nitrido complexes were prepared: [LV(V)(N)(acac)](ClO(4)) (6), [LCr(V)(N)(acac)](ClO(4)) (13), [LCr(V)(N)(tacac)](ClO(4)) (14), [LCr(V)(N)(pic)](ClO(4)) (15), [LCr(V)(N)(phen)](ClO(4))(2) (16), [LCr(V)(N)(ox)] (19), [L'Mn(V)(N)(acac)]PF(6) (21). Photolysis of [LCr(III)(N(3))(ox)] (17) in the solid state produces the &mgr;-nitrido-bridged mixed-valent species [L(2)Cr(2)(ox)(2)(&mgr;-N)](N(3)) (18). The structures of the precursor complex [L'Mn(acac)(N(3))]BPh(4) (20), of 13, and of [L'Mn(V)(N)(acac)]BPh(4) (21) have been determined by X-ray crystallography. Complex 13 crystallizes in the orthorhombic space group Pnma, with cell constants a = 27.187(5) ?, b = 9.228(2) ?, c = 7.070(1) ?, V = 1773.7(6) ?(3), and Z = 4; complex 20 crystallizes in the triclinic space group P&onemacr; with a = 14.769(5) ?, b = 16.83(1) ?, c = 16.96(1) ?, alpha = 108.19(5) degrees, beta = 105.06(4) degrees, gamma = 99.78(4) degrees, V = 3719(2) ?(3), and Z = 4; and complex 21 crystallizes in the monoclinic space group P2(1)/n with a = 10.443(3) ?, b = 16.035(4) ?, c = 21.463(5) ?, beta = 95.76(1) degrees, V = 3575.9(14) ?(3), and Z = 4. The Cr(V)&tbd1;N and Mn(V)&tbd1;N distances are short at 1.575(9) and 1.518(4) ?, respectively, and indicate a metal-to-nitrogen triple bond.     

Dinuclear complexes of chiral tetradentate pyridylimine ligands: diastereoselectivity, positive cooperativity, anion selectivity, ligand self-sorting based on chirality, and magnetism

The synthesis and coordination chemistry of two chiral tetradentate pyridylimine Schiff base ligands are reported. The ligands were prepared by the nucleophilic displacement of both bromides of 1,3-bis(bromomethyl)benzene (2) or 3,5-bis(bromomethyl)toluene (3) by the anion of (S)-valinol, followed by capping of both amine groups with pyridine-2-carboxaldehyde. Both ligands react with CoCl(2) and NiCl(2) to give [M(2)L(2)Cl(2)](2+) complexes. Remarkably, neither fluoride nor bromide ions can act as bridging ligands. The formation of [Co(2)((S)-3)(2)Cl(2)](2+) is highly diastereoselective, and X-ray crystallography shows that both metal centers in the [Co(2)((S)-3)(2)Cl(2)](CoCl(4)) complex adopt the lambda configuration (crystal data: [Co(2)(C(31)H(40)N(4)O(2))(2)Cl(2)](CoCl(4)).(CH(3)CN)(3), monoclinic, P2(1), a = 11.595(2) A, b = 22.246(4) A, c = 15.350(2) A, V = 3705(1) A(3), beta = 110.643(3) degrees, Z = 2). Structurally, the dinuclear complex can be viewed as a helicate with the helical axis running perpendicular to the [Co(2)Cl(2)] plane. The reaction of racemic 2 with CoCl(2) was shown by (1)H NMR spectroscopy to yield a racemic mixture of Lambda,Lambda-[Co(2)((S)-2)(2)Cl(2)](2+) and delta,delta-[Co(2)((R)-2)(2)Cl(2)](2+) complexes; that is, a homochiral recognition process takes place. Spectrophotometric titrations were performed by titrating (S)-3 with Co(ClO(4))(2) followed by Bu(4)NCl, and the global stability constants of [Co((S)-3)](2+) (log beta(110) = 5.7), [Co((S)-3)(2)](2+) (log beta(120) = 11.6), and [Co(2)((S)-3)(2)Cl(2)](2+) (log beta(110) = 23.8) were calculated. The results revealed a strong positive cooperativity in the formation of [Co(2)((S)-3)(2)Cl(2)](2+). Variable-temperature magnetic susceptibility curves for [Co(2)((S)-2)(2)Cl(2)](BPh(4))(2) and [Co(2)((S)-3)(2)Cl(2)](BPh(4))(2) are very similar and indicate that there are no significant magnetic interactions between the cobalt(II) centers.     

Coordination-position isomeric M(II)Cu(II) and Cu(II)M(II) (M = Co, Ni, Zn) complexes derived from macrocyclic compartmental ligands

The dinucleating macrocyclic ligands (L(2;2))(2-) and (L(2;3))(2-), comprised of two 2-[(N-methylamino)methyl]-6-(iminomethyl)-4-bromophenolate entities combined by the -(CH(2))(2)- chain between the two aminic nitrogen atoms and by the -(CH(2))(2)- or -(CH(2))(3)- chain between the two iminic nitrogen atoms, have afforded the following M(II)Cu(II) complexes: [CoCu(L(2;2))](ClO(4))(2).MeCN (1A), [NiCu(L(2;2))](ClO(4))(2) (2A), [ZnCu(L(2;2))](ClO(4))(2).0.5MeCN.EtOH (3A), [CoCu(L(2;3))(MeCN)(2-PrOH)](ClO(4))(2) (4A), [NiCu(L(2;3))](ClO(4))(2) (5A), and [ZnCu(L(2;3))](ClO(4))(2).1.5DMF (6A). [CoCu(L(2;2))(MeCN)(3)](ClO(4))(2) (1A') crystallizes in the monoclinic space group P2(1)/n, a = 11.691(2) A, b = 18.572(3) A, c = 17.058(3) A, beta= 91.18(2) degrees, V = 3703(1) A(3), and Z = 4. [NiCu(L(2;2))(DMF)(2)](ClO(4))(2) (2A') crystallizes in the triclinic space group P(-)1, a = 11.260(2) A, b = 16.359(6) A, c = 10.853(4) A, alpha= 96.98(3) degrees, beta= 91.18(2) degrees, gamma= 75.20(2) degrees, V = 1917(1) A(3), and Z = 2. 4A crystallizes in the monoclinic space group P2(1)/c, a = 15.064(8) A, b = 11.434(5) A, c = 21.352(5) A, beta= 95.83(2)degrees, V = 3659(2) A(3), and Z = 4. The X-ray crystallographic results demonstrate the M(II) to reside in the N(amine)(2)O(2) site and the Cu(II) in the N(imine)(2)O(2) site. The complexes 1-6 are regarded to be isomeric with [CuCo(L(2;2)))](ClO(4))(2).DMF (1B), [CuNi(L(2;2)))](ClO(4))(2).DMF.MeOH (2B), [CuZn(L(2;2)))](ClO(4))(2).H(2)O (3B)), [CuCo(L(2;3)))](ClO(4))(2).2H(2)O (4B), [CuNi(L(2;3)))](ClO(4))(2) (5B), and [CuZn(L(2;3)))](ClO(4))(2).H(2)O (6B) reported previously, when we ignore exogenous donating and solvating molecules. The isomeric M(II)Cu(II) and Cu(II)M(II) complexes are differentiated by X-ray structural, magnetic, visible spectroscopic, and electrochemical studies. The two isomeric forms are significantly stabilized by the "macrocyclic effect" of the ligands, but 1A is converted into 1B on an electrode, and 2A is converted into 2B at elevated temperature.