Assembly of cyano-bridged Cu(II)/Cu(II) and Cu(I)/Cu(II) compounds obtained by controlled ration of cyanide

One reaction system of Cu²⁺, dipn, and CN⁻ with two different molar ratio sets of 1:1:5, and 2:1:8 produced two compounds 1 [Cu^II(dipn)][Cu^II(CN)₄], and 2, respectively (dipn = dipropylenetriamine). Their structures were determined by X-ray crystallography. Compound 2 is built from Cu(I) and Cu(II) centers, which are bridged by cyanide groups and metal-metal bonds. The magnetic properties of 1 and 2 were investigated in 2-300 K. Compound 1 exhibits an antiferromagnetic exchange interaction between copper(II) ions mediated by cyano-bridges.     

Synthesis and characterization of Cu(I) and Cu(II) complexes containing ketiminate ligands

A series of Cu(I) and Cu(II) complexes containing substituted ketiminate ligands was synthesized. Reaction of CuCl₂ with 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] in toluene generated dark green solid of Cu[OC(Me)CHC(Me)N(Ar)]₂ (1). Similarly, Cu(I) complex, {Cu[OC(Me)CHC(Me)N(Ar)]Li[OC(Me)CHC(Me)N(Ar)]}₂ (2) was synthesized by reacting 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] with CuCl in toluene at room temperature for 12 h. While the reaction of CuCl with Li[OC(Me)CHC(Me)N(Ar)] in the presence of triphenylphosphine in THF solution at room temperature, a three-coordinated Cu[OC(Me)CHC(Me)N(Ar)](PPh₃) (3) can be isolated in high yield. Replacing the PPh₃ of 3 with N-heterocarbene (NHC) generates Cu[OC(Me)CHC(Me)N(Ar)](NHC) (4) in low yield. Complexes 2, 3, and 4 were characterized by ¹H and ¹³C NMR spectroscopies and all molecules were structurally characterized by X-ray diffractometry. Two coordination modes of ketiminate ligands were found in the molecular structure of 2, one of which is copper-coordinated terminal ketiminates and the other is lithium-copper-coordinated bridging ketiminates.     

Influence of synthesis condition on product formation: hydrothermal auto-oxidated synthesis of five copper halides with ratio of Cu(I)/Cu(II) in 1:1, 2:1, 3:1, 4:1 and 1:0

The hydrothermal synthesis and structural characterization of five copper iodides derived from chelated ligands, 1, 10-phenanthroline (phen), ethylenediamine (en) and 1, 3-propanediamine, are reported. Except monovalent copper compound 1 ((phen)Cu₃I₃1), other four compounds ([Cu(phen)₂I][CuI₂] 2, [Cu(phen)₂I][Cu₃I₄] 3, [Cu(en)₂][Cu₄(phen)₂I₆] 4 and [Cu(1, 3-propanediamine)₂][CuI₂]₂5) are mixed-valent Cu(I)-Cu(II) compounds by partially auto-oxidated from Cu(I). Supramolecular frameworks of these compounds can be assembled by C/N-H?I hydrogen bonds, Cu(I)-Cu(I) interaction, weak Cu-I semicoordinate interaction, C-H?π and π-π stacking interactions. It's noteworthy that we find hydrothermal synthesis under higher pH value, higher synthesis temperature and longer reaction time can obtain higher ratio of Cu(I)/Cu(II) copper iodides and organic ligand with lower steric hinderance is prone to coordinated with divalent copper to form cation unit. Finally, the fluorescent study shows 1 exhibits intense orange-red luminescence with long lifetime at 293 K and more intense emission and longer lifetime at 77 K. Moreover, the room temperature EPR spectra of above five compounds not only show the valence of copper but demonstrate the coordination environment of Cu(II) centre.     

Syntheses and crystal structures of straight or zigzag one-dimensional coordination polymers based on Cu(II) square pyramidal or Cu(I) tetrahedral coordination environments

Two coordination polymers containing copper ions, [Cu(SO₄)(pyz)(H₂O)]_n (1) and [Cu₂(SO₄)(pyz)₂(H₂O)₂]_n (2) (pyz = pyrazine), have been synthesized and characterized by single-crystal X-ray analyses. Compound 1 was synthesized by the reaction of Cu(SO₄) · 5H₂O with pyz (ratio = 1:2) in H₂O at room temperature. The structure of 1 consists of linear chains of [Cu(pyz)(H₂O)]²⁺, with coordinated sulfate ions bridging the chains. Compound 2 was obtained as dark red blocks from the reaction of Cu(SO₄) · 5H₂O and pyz (ratio = 1:2) in H₂O, after heating to 180 °C in a Teflon autoclave for 48 h. The structure of 2 consists of zigzag chains of [Cu(pyz)(H₂O)]⁺ with sulfate ions. Only the difference in the synthesis temperature, room temperature or 180 °C, determines whether Cu(II) or Cu(I) coordination polymers are formed, with the reduction of Cu(II) to Cu(I) being explained by the Gillard mechanism.     

Syntheses, crystal structures and magnetic properties of two dicopper(II) complexes and a zigzag 1-D Cu(II) complex of a bidentate pyridyl-pyrazole ligand

Two new dinuclear copper compounds, [Cu₂(pypz)₂(N₃)₂(NO₃)₂] (1) and [Cu₂(pypz)₂(OH)₂(NO₃)₂] (2), and one 1-D polymeric Cu(II) complex, [Cu(pypz)(dca)₃]_n (3) [‘pypz’ = (3,5dimethyl-1-(2′-pyridyl)pyrazole) and dca = (dicyanamide)], have been synthesized and characterized crystallographically and spectroscopically. Complex 1 is pseudo-octahedral, adjacent Cu atoms are connected by a pair of μ(1,1) azido groups and the structure is stabilized by π-π interactions between two pyridyl moieties from two different neighboring complex molecules. Complexes 2 and 3 are square pyramidal. The hydroxo bridged complex 2 is further stabilized through H-bonding. The 1-D polymeric chain of 3 is bridged by an end-to-end dicyanamide bridge and it propagates along the crystallographic b axis, whilst the polymer chains are stacked one upon another along the crystallographic c axis. Low temperature magnetic measurement shows that complexes 1 and 2 are ferromagnetic (J values are 30.81 and 14.79 cm⁻¹, respectively), whereas due to larger Cu-Cu distances, complex 3 shows weak ferromagnetism.     

Structural diversity in Cu(II), Cd(II) and Hg(II) coordination complexes with the rigid N,N′-bis(2/3-aryl)-1,4-benzenedicarboxamide ligand

The syntheses and structures of a series of metal complexes, namely Cu₂Cl₄(L¹)(DMSO)₂·2DMSO (L¹ = N,N′-bis(2-pyridinyl)-1,4-benzenedicarboxamide), 1; {[Cu(L²)_1.5(DMF)₂][ClO₄]₂·3DMF}_∞ (L² = N,N′-bis(3-pyridinyl)-1,4-benzenedicarboxamide), 2; {[Cd(NO₃)₂(L³)]·2DMF}_∞ (L³ = N,N′-bis-(2-pyrimidinyl)-1,4-benzenedicarboxamide), 3; {[HgBr₂(L³)]·H₂O}_∞, 4, and {[Na(L³)₂][Hg₂X₅]·2DMF}_∞ (X = Br, 5; I, 6) are reported. All the complexes have been characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Complex 1 is dinuclear and the molecules are interlinked through S?S interactions. In 2, the Cu(II) ions are linked through the L² ligands to form 1-D ladder-like chains with 60-membered metallocycles, whereas complexes 3 and 4 form 1-D zigzag chains. In complexes 5 and 6, the Na(I) ions are linked by the L³ ligands to form 2-D layer structures in which the [Hg₂X₅]⁻ anions are in the cavities. The L² ligand acts only as a bridging ligand, while L¹ and L³ show both chelating and bridging bonding modes. The L¹ ligand in 1 adopts a trans-anti conformation and the L² ligand in 2 adopts both the cis-syn and trans-anti conformations, whereas the L³ ligands in 3–6 adopt the trans conformation.     

Synthesis and coordination chemistry of new tetradentate N2S2 donor Schiff-base ligand ca2-dapte: Mononuclear and dinuclear copper(I) complexes [Cu(ca2dapte)]ClO4 and [{Cu(PPh3)(X)}2(ca2dapte)] (X = I and Br)

A mononuclear copper(I) complex, [Cu(ca₂dapte)]ClO₄ (1), and two dinuclear copper(I) complexes, [{Cu(PPh₃)(X)}₂(ca₂dapte)] (X = I (2) and Br (3)), of a new tetradentate N₂S₂ donor Schiff-base ligand ca₂dapte have been prepared (ca₂dapte = N,N′-bis(trans-cinnamaldehyde)-1,2-di(o-iminophenylthio)ethane). These compounds have been characterized by elemental analyses (CHN), FT-IR, UV–Vis and ¹H NMR spectroscopy. The crystal structures of these copper(I) complexes have been determined by single-crystal X-ray diffraction. The coordination geometry around Cu(I) centers in these complexes is a distorted tetrahedron. The ca₂dapte is coordinated to Cu(I) as a tetradentate ligand in 1, while it acts as a bis-bidentate bridging ligand in 2 and 3.     

“Wheel-and-axle” binuclear Cu(II) dioximates mediated by 1,2-bis(4-pyridyl)ethane: Synthesis, X-ray study and luminescent properties

The reaction of copper(II) acetate or fluoride with classic dioximes in the presence of 1,2-bis(4-pyridyl)ethane resulted in four novel compounds with the compositions [Cu₂(dmgH)₄bpe] (1), [Cu₂(NioxH)₄bpe] (2), [Cu₂(dpgH)₄bpe] (3), and [Cu₂(dpgH)₄bpe][Cu(dpgH)₂bpe]₂·2DMF (4) (where dmgH₂ = dimethylglyoxime, NioxH₂ = 1,2-cyclohexanedionedioxime, dpgH₂ = diphenylglyoxime, bpe = 1,2-bis(4-pyridyl)ethane, and DMF = N,N′-dimethylformamide), whose crystal structures were determined by single crystal X-ray diffraction. In the binuclear molecules 1-3, as well as in both binuclear and mononuclear molecules in 4 each Cu(II) atom has an identical N₅-environment formulated by four oximic nitrogen atoms of two monodeprotonated ligands in a slightly distorted square planar mode, and the nitrogen atom of the bpe molecule being in the apical position. The new compounds were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Luminescence investigations for 1, 2 and 4 were carried out to clarify whether the guest inclusion in the crystal lattice is accompanied by changes in the emission spectra.     

Exploring the reactivity of an N-pyrazole, P-phosphine hybrid ligand with Cu(I), Ag(I) and Au(I) precursors

The reactivity of (3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphine (L) hybrid ligand against Cu(I), Ag(I) and Au(I) has been assayed and compounds [Cu(L)₂](PF₆) (1), [Ag(L)]₂(PF₆)₂·2C₂H₄Cl₂·2C₄H₁₀O (2) and [AuCl(L)]₂ (3) have been isolated and fully characterised. A fully characterisation by analytical and spectroscopic methods of 1-3 are presented and X-ray crystal structures of 1 and 2 are also reported. The similar data obtained between 2 and 3 permits to do a serious purpose of the structure of 3 in solid and solution.     

Self assembly of asymmetric tetranuclear Cu(II) [2 × 2] grid-like complexes and of a dinuclear Ni(II) complex from pyridyl-phenol Schiff base ligands

Self assembly of N-salicylidene 2-aminopyridine (L1H) with Cu(NO₃)₂·3H₂O affords [Cu₄(L1)₄(NO₃)₃(CH₃OH)][Cu(L1)(NO₃)₂](2-aminopyridinium)(NO₃)·5CH₃OH (1) which is composed of an asymmetric [2 × 2] grid-like cationic complex that co-crystallizes with a Cu(II) mononuclear anion. This remarkable tetranuclear unit presents three penta-coordinated and one hexa-coordinated Cu(II) sites. This quadruple helicate structure reveals strong anti-ferromagnetic coupling (J = −340(2) cm⁻¹) between Cu(II) ions through a double alkoxo bridge. Reacting L1H with Cu(NO₃)₂·3H₂O in slightly different conditions affords however a more symmetric tetranuclear grid-like complex: [Cu₄(L1)₄(NO₃)₂(OH)₂](2-aminopyridinium)(OH)·CH₃OH) (2). A dinuclear Ni(II) complex, [Ni₂(L2)₂(L2H)₂(NCS)₂(CH₃OH)₂]·2CH₃OH (3), obtained with another related donor ligand (L2H = N-salicylidene 3-aminomethylpyridine) was also prepared.     

Solvothermal syntheses and crystal structures of new Cu(II) complexes with phenylsuccinic acid

Five new Cu(II) complexes [Cu(psa)(phen)] · 3H₂O (1), [Cu(psa)(2bpy)] · 0.5H₂O (2), [Cu(psa)(2bpy)(H₂O)] · 3H₂O (3), [Cu(psa)(4bpy)] · H₂O (4), and [Cu(psa)_0.5(N₃)(2bpy)] (5) (H₂psa = phenylsuccinic acid, phen = 1,10-phenanthroline, 2bpy = 2,2′-bipyridine, and 4bpy = 4,4′-bipyridine) were obtained under solvothermal conditions and characterized by single-crystal X-ray diffraction. Complexes 2 and 3 were formed by one-pot reaction. In complex 2, Cu(II) ion is four-coordinated and locates at a slightly distorted square center. In complex 3, the coordinated water molecule occupies the axial site of Cu(II) ion forming a tetragonal pyramid geometry. Complexes 1 and 3 are of 1D chain structures, and extended into 2D supramolecular network by hydrogen bonds. Complex 2 is of zipper structure, and further assembled into 2D supramolecular network by hydrogen bonds and π–π stacking interactions. Complex 4 is a 3D CdSO₄-like structure with twofold interpenetration, while complex 5 is a dinuclear compound. The different structures of complexes 1–5 can be attributed to using the auxiliary ligands, indicating an important role of the auxiliary ligands in assembly and structure of the title complexes.     

Dinuclear copper(I) complexes of tris(3,5-dimethylpyrazol-1-yl)methane: Synthesis, structure, and reactivity

The reaction of [Cu(NCMe)₄](BF₄) with equimolar amounts of the tris(substituted-pyrazolyl)methane ligand HCPz₃ or HC(3,5-Me₂Pz)₃ yields the respective salts [Cu(HCPz₃)(NCMe)](BF₄) (1a) or [Cu(HC(3,5-Me₂Pz)₃)(NCMe)](BF₄) (1). The acetonitrile ligand of 1 can be replaced by prazine, 4,4′-dipyridine or 1,4-diisocyanobenzene to yield related mononuclear complexes [Cu(HC(3,5-Me₂Pz)₃)(pyrazine)](BF₄) (2), [Cu(HC(3,5-Me₂Pz)₃)(4,4′-bipyridine)] (BF₄) (3) or [Cu(HC(3,5-Me₂Pz)₃)(1,4- CNC₆H₄NC)](BF₄) (7), respectively. A series of binuclear copper(I) complexes {[Cu(HC(3,5-Me₂Pz)₃)]₂(μ -BL)}(BF₄)₂ (4, BL = pyrazine; 5, BL = 4,4′-dipyridine; 8, BL = 1,4-diisocyanobenzene) were prepared by treating equal molar ratio of 1 with related mononuclear complexes 2, 3 and 7. In addition, binuclear copper(I) complexes were also prepared from treatment of 2 equiv of 1 with the related bridge ligand. Both of 4 and 5 reformed mononuclear starting complex 1 in acetonitrile solution. However, the more robust complex 8 was stable in acetonitrile solutions. The structure of complexes 1a, 4, 5, and 7 were confirmed by X-ray crystallography. The redox properties of 4 and 8 were examined by cyclic voltammetry and exhibited two quasi-reversible waves suggesting that no significant structural reorganization occurs during the redox process on the electrochemical time scale.     

Hetero-metallic frameworks of [Pd(CN)4] and Cu(II) with triamines: A rare example of a tetracyanometallate bridged 2D coordination polymer

Four cyano bridged Cu(II)–Pd(II) heterometallic complexes, [Cu(dpt)Pd(CN)₄]_n (1), {[Cu₂(medpt)₂Pd(CN)₄](ClO₄)₂ · 3H₂O}_n (2), {[Cu₂(dien)₂Pd(CN)₄](ClO₄)₂ · 2CH₃OH}_n (3) and {[Cu₂(iPrdien)₂Pd(CN)₄](ClO₄)₂ · 2H₂O}_n (4) [dpt = 3,3′-iminobispropylamine; medpt = 3,3′-diamino-N-methyldipropylamine; dien = diethylenetriamine and iprdien = N′-isopropyldiethylenetriamine] have been synthesized and characterized by single crystal X-ray diffraction analysis, magnetic measurement and thermal study. Complexes 1, 2 and 3 are 1D coordination polymers, while 4 presents a 2D network. In 1, the cis-directed cyanide ligands of [Pd(CN)₄]²⁻ anions link two Cu(dpt) units to form a neutral coordination polymer, whereas in 2, 3 and 4, all the cyanide groups of [Pd(CN)₄]²⁻ take part in bonding with four adjacent Cu(II) ions, resulting in cationic coordination polymers counterbalanced by perchlorate anions. The structures are compared with those of analogous [Ni(CN)₄]²⁻ derivatives. The magnetic behavior shows antiferromagnetic interactions in all the complexes.     

Syntheses, structures and ligand conformations of Cu(II), Co(II) and Ag(I) complexes containing the phosphinic amide ligands

The syntheses, structures and ligand conformations of the complexes trans-Cu(L1)₂(ClO₄)₂, (L1 = N-(2-pyrimidinyl)-P,P-diphenyl-phosphinic amide), 1, [trans-Co(L1)₂(CH₃OH)₂](ClO₄)₂·O(C₂H₅)₂, 2, [trans-Co(L2)₂(H₂O)₂](ClO₄)₂·2CH₃OH, (L2 = N-(2-pyridinyl)-P,P-diphenyl-phosphinic amide), 3, [cis-Co(L2)₂(NO₃)](NO₃), 4, and [Ag(L3)(NO₃)(CH₃CN)]_∞, (L3 = N-(6-methyl-2-pyridinyl)-P,P-diphenyl-phosphinic amide), 5, are reported. The L1 and L2 ligands in the monomeric complexes 1-4 chelate the metal centers through the pyrimidyl/pyridyl nitrogen atoms and the phosphinic amide oxygen atoms, whereas the L3 ligands in complex 5 bridge the metal centers, forming a 1-D zigzag chain. The chelating L2 ligands in complexes 3 and 4 adopt cis conformations and the bridging L3 ligand in complex 5 adopts a trans conformation, respectively.     

Copper(I) and silver(I) complexes of 1,5-methylene- and diethylmethylene-bridged bis(oxazoline) ligands. In situ Cu(II)-catalyzed oxidation of methylene bridge

Silver(I) and copper(I) complexes of C₂-symmetric bis(oxazoline) ligands were studied by UV, NMR, IR, EPR and ES-MS spectroscopies. The stability constants of the Ag-1a and Ag-1b complexes with 1:1 and 1:2 stoichiometries in acetonitrile were determined by NMR spectrometric titrations. The evidence of tetrahedral coordination for complex (Ag(1a)₂(⁺ was obtained from the complexation induced shifts (CIS) and NOEs. Mass spectra revealed the Cu(II) mediated oxidation of methylene bridge in copper complexes of 1a and 1b, which was in accordance with the UV, NMR, IR and EPR findings. The efficiency of Cu(I) complexes of methylene-bridged 1,5-bis(oxazoline)s 1 as chiral catalysts in stereoselective cyclopropanation of styrene with ethyl diazoacetate, was compared to that of the dialkylmethylene-bridged 1,5-bis(oxazoline)s 2.     

Assembly molecular architectures based on structural variation of metalloligand [Cu(PySal)2] (PySal = 3-pyridylmethylsalicylideneimino)

A versatile neutral metalloligand [Cu(PySal)₂] (1) (PySal = 3-pyridylmethylsalicylidene-imino) was exploited as a building unit to construct five complexes {Cu[Cu(PySal)₂]₂}(ClO₄)₂ (2), {Cd[Cu(PySal)₂]₂(H₂O)₂]} (NO₃)₂ · 2H₂O · 4CH₃OH (3), {Zn[μ₂-Cu(PySal)₂]Cl₂}_n · nCH₃OH (4), {Hg[μ₂-Cu(PySal)₂]I₂}_n (5) and {Cd[μ₂-Cu(PySal)₂]Cl₂}_n · nCH₂Cl₂ (6). [Cu(PySal)₂] acts as a chelating ligand in discrete complexes 2 and 3 with unbound anions, but as a bis-monodentate bridging ligand in polymers 4, 5 and 6 when halogen anions coordinated cooperatively to metal cations. The coordination geometry of Cu²⁺ is well-defined square planar in bridging [Cu(PySal)₂], analogous to that in free metalloligand (1), but it is distorted square planar in chelating [Cu(PySal)₂].     

Cu(I) catalysed cyclopropanation of olefins: Stereoselectivity studies with Arylid-Box and Isbut-Box ligands

In our quest to find new ligands for highly stereoselective reactions, we tested a variety of chiral non-racemic pseudo-C₂ symmetric bis-oxazolines derived from malonic acid containing an arylidene bridge unit (and appropriately termed Arylid-Box) in the catalytic asymmetric cyclopropanation (CAP) reaction of styrene and ethyl diazoacetate using between only 1-2 mol% of a Cu(I) pre-catalyst. Some very good e.e.s (up to 86%), were obtained. It was possible to isolate 10a′-[Cu(CH₃CN)₄]PF₆ which existed as a bench stable solid that proved to be more efficient than the catalyst prepared in situ. Cu(I) pre-catalysts were used for the first time in the CAP reaction with the Isbut-Box ligands 13a and 13b and, although, the e.e.s were better for ligand 13a using these pre-catalysts, in the case of ligand 11b this was not the case. Spectroscopic studies (UV-Vis and ¹H NMR) were carried out to gain an insight into the nature of the catalytic species at work so that the conditions could be optimised giving better results. Some theoretical studies were conducted to try to explain the better enantioselectivities obtained using Evans’ tert-Box-Cu(I) complex over our complex.     

3D-supramolecular copper(I) cyanide coordination polymers through hydrogen bonding

The reactions of K₃[Cu(CN)₄], 3-acetylpyridine (3-Acpy) or 4-acetylpyridine (4-Acpy) in the presence of Me₃SnCl in H₂O/acetonitrile media at room temperature afford the 3D-supramolecular coordination polymers (SCPs)_∞³[Cu₂CN(μ-CN)·(3-Acpy)₂] 1 and _∞³[Cu₂CN(μ-CN)·(4-Acpy)₂] 2. The structures of 1 and 2 consist of Cu₂CN building blocks which are connected by CN groups, forming 1D-zig-zag chains. Each chain is bonded to another chain by hydrogen bonding into a 2D-layer, which is further stacked in an interwoven mode by π–π stacking interactions and hydrogen bonds in 1 and 2, as well as Cu···Cu interactions in 1, to create supramolecular 3D-network structures. The high dimensional topologies of 1 and 2 result mainly from extensive hydrogen bonding and π–π stacking. The long wavelength absorption band at 400–420 nm in the electronic spectra of 1 and 2 is assigned to a CT from copper(I) to the Acpy ligand. Compound 2 exhibits strong luminescence at 485 and 527 nm, corresponding to MLCT and metal-centered transitions, respectively.     

Assembly and structures of five new Cu(II) complexes based on the V-shaped building block [Cu(dbsf)]

Five new copper(II) complexes [Cu(dbsf)(H₂O)]_n · 0.5n(i-C₃H₇OH) (1), [Cu(dbsf)(4,4′-bpy)_0.5]_n · nH₂O (2), [Cu(dbsf)(2,2′-bpy)(H₂O)]₂ · (n-C₃H₇OH) · 0.5H₂O (3), [Cu(dbsf)(phen)(H₂O)]₂ · 1.5H₂O (4) and [Cu(dbsf)(2,2′-bpy)(H₂O)]_n · n(i-C₃H₇OH) (5) (H₂dbsf = 4,4′-dicarboxybiphenyl sulfone, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, i-C₃H₇OH = isopropanol, n-C₃H₇OH = n-propanol) have been synthesized under hydro/solvothermal conditions. All of the complexes are assembled from V-shaped building blocks, [Cu(dbsf)]. Complex 1 is composed of 1D double-chains. In complex 2, dbsf²⁻ ligands and 4,4′-bpy ligands connect Cu(II) ions into catenane-like 2D layers. These catenane-like 2D layers stack in an ABAB fashion to form a 3D supramolecular network. Complexes 3 and 4 are 0D dimers, in which two [Cu(dbsf)] units encircle to form dimetal macrocyclic molecules. However, in complex 5, the V-shaped building blocks [Cu(dbsf)] are joined head-to-tail, resulting in the formation of infinite tooth-like chains. The different structures of complexes 3 and 5 may be attributed to the different solvent molecules included.     

Copper(II) complexes of tridentate selenobisphenolate ligand in mixed ligand environments: Synthesis, crystal structure, EPR and electrochemical studies

A series of square-pyramidal copper(II) complexes, [Cu(L^Se)(N^∧N)] (H₂L^Se = seleno-bisphenolate; N^∧N = bipyridyl, phenanthroline or N,N-dimethylethylenediamine) have been synthesized and characterized by elemental analyses, magnetic measurements, IR, EPR, and electronic spectral studies. Single crystal X-ray structures of [Cu(L^Se)(bpy)]·H₂O (2), [Cu(L^Se)(phen)]·CH₂Cl₂ (3) and [Cu(L^Se)(N,N-Me₂en)] (4) showed that all the complexes have approximately square-pyramidal geometry. In complexes 2 and 3, the square plane is occupied by O(1), O(2), N(1) and N(2) and the apical position by Se atom of L^{Se 2−} ligand. The asymmetric unit of complex 4 contains two crystallographically independent discrete molecules A and B with CuN₂OSe chromophore comprising the square plane and the axial position being occupied by another phenolate oxygen atom. Complexes 2, 3 and 4 are found to be paramagnetic and EPR parameters extracted are: g_∥ = 2.232, g_⊥ = 2.069; 〈g_eff〉 = 1.95; and g_∥ = 2.232, g_⊥ = 2.083 for complexes 2, 3 and 4, respectively. Both the complexes 2 and 4 show three reduction processes: (a) a quasi-reversible reduction of Cu^II to Cu^I, (b) an irreversible reduction of Cu^I to Cu⁰ with the release of free ligand, and (c) a reduction process occurs at this coordinated ligand. They also show a well-defined quasi-reversible oxidation of Cu^II to Cu^III and an irreversible oxidation peak at ∼1.30 and 1.40 V vs. Ag/AgCl for 4 and 2, respectively, with no cathodic counterpart, and were attributed to the oxidation of the metal coordinated ligand.