A kinetics and mechanistic study on the role of the structural rigidity of the linker on the substitution reactions of chelated dinuclear Pt(II) complexes

Substitution reactions of platinum complexes bearing cyclohexylamine/diamine moieties viz., [Pt(H(2)O)(N,N-bis(2-pyridylmethyl)cyclohexylamine)](CF(3)SO(3))(2), bpcHna; [{Pt(H(2)O)}(2)(N,N,N',N'-tetrakis(2-pyridylmethyl)-trans-1,4-cyclohexyldiamine)](CF(3)SO(3))(4), cHn and [{Pt(H(2)O)}(2)(N,N,N',N'-tetrakis(2-pyridylmethyl)-4,4'-dicyclohexylmethanediamine)](CF(3)SO(3))(4), dcHnm and phenylamine/diamine moieties viz., ([Pt(H(2)O)N,N-bis(2-pyridylmethyl)phenylamine)](CF(3)SO(3))(2), bpPha; [{Pt(H(2)O)}(2)(N,N,N',N'-tetrakis(2-pyridylmethyl)-1,3-phenyldiamine)](CF(3)SO(3))(4), mPh; [{Pt(H(2)O)}(2)(N,N,N',N'-tetrakis(2-pyridylmethyl)-1,4-phenyldiamine)](CF(3)SO(3))(4), pPh and [{Pt(H(2)O)}(2)(N,N,N',N'-tetrakis(2-pyridylmethyl)-4,4'-diphenylmethanediamine)](CF(3)SO(3))(4)), dPhm with thiourea nucleophiles were studied in acidified 0.01 M LiCF(3)SO(3) aqueous medium under pseudo-first-order conditions using stopped-flow and UV-visible spectrophotometric techniques. The rate of substitution follows a similar trend in the two sets of complexes and decreases in the order: bpcHna > dcHnm > cHn and bpPha > dPhm ≈ pPh ≈ mPh), respectively. The result of this study has shown that the rigidity and/or the planarity of a diamine bridge linking the two (2-pyridylmethyl)amine-chelated Pt(II) centres, influences the reactivity of the metal centres by protracting similar symmetry elements within the complexes, which determines the amount of steric influences felt on the coordination square-plane. Hence, the order of reactivity is controlled by both the steric hindrance and the magnitude of the trans σ-inductive effect originating from the linker towards the metal centre. These two factors also impact on the acidity of the complexes. The high negative entropies and low positive enthalpies support an associative mode of activation.     

Ion-pair interactions of lanthanide(III) complexes in aqueous solutions

The formation of ion-pair adducts between the cationic complex La(THP)3+ (THP = 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane) and the anionic complexes Tm(DOTA)- (DOTA = 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetate), Tm(DTPA)2- (DTPA = diethylenetriamine-N,N,N',N",N"-pentaacetate), Tm(TTHA)3- (TTHA = triethylenetetraamine-N,N,N',N",N"',N"'-hexaacetate), and Tm(DOTP)5- (DOTP = 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetrakis(methylenephosphonate)) is examined by 13C NMR spectroscopy. The induced 13C shifts of the La(THP)3+ complex are followed by titration of the Tm(III) complexes of DOTA, DTPA, and TTHA at pH 7. From these data, the stability constants are calculated to be beta 1 = 64 M-1 (1:1), beta 1 = 296 M-1 (1:1), and beta 2 = 26,000 M-2 (2:1) for the ion pairs of La(THP)3+, with Tm(DOTA)-, Tm(DTPA)2-, and Tm(TTHA)3-, respectively. The La(THP)3+,Tm(DOTP)5- system elicits chiral resolution of the rapidly interconverting Tm(DOTP)5- isomers.     

Thermochemistry of N-N containing ions: a threshold photoelectron photoion coincidence spectroscopy study of ionized methyl- and tetramethylhydrazine

The unimolecular dissociation reactions of the methylhydrazine (MH) and tetramethylhydrazine (TMH) radical cations have been investigated using tandem mass spectrometry and threshold photoelectron photoion coincidence spectroscopy in the photon energy ranges 9.60-31.95 eV (for the MH ion) and 7.74-29.94 eV (for the TMH ion). Methylhydrazine ions (CH3NHNH2(+*)) have three low-energy dissociation channels: hydrogen atom loss to form CH2NHNH2(+) (m/z 45), loss of a methyl radical to form NHNH2(+) (m/z 31), and loss of methane to form the fragment ion m/z 30, N2H2(+*). Tetramethylhydrazine ions only exhibit two dissociation reactions near threshold: that of methyl radical loss to form (CH3)2NNCH3(+) (m/z 73) and of methane loss to form the fragment ion m/z 72 with the empirical formula C3H8N2(+*). The experimental breakdown curves were modeled with Rice-Ramsperger-Kassel-Marcus theory, and it was found that, particularly for methyl radical loss, variational transition state theory was needed to obtain satisfactory fits to the data. The 0 K enthalpies of formation (delta(f)H0) for all fragment ions (m/z 73, m/z 72, m/z 45, m/z 31, and m/z 30) have been determined from the 0 K activation energies (E0) obtained from the fitting procedure: delta(f)H0[(CH3)2NNCH3(+)] = 833 +/- 5 kJ mol(-1), delta(f)H0 [C3H8N2(+*)] = 1064 +/- 5 kJ mol(-1), delta(f)H0[CH2NHNH2(+)] = 862 +/- 5 kJ mol(-1), delta(f)H0[NHNH2(+)] = 959 +/- 5 kJ mol(-1), and delta(f)H0[N2H2(+*)] = 1155 +/- 5 kJ mol(-1). The breakdown curves have been measured from threshold up to h nu approximately 32 eV for both hydrazine ions. As the photon energy increases, other dissociation products are observed and their appearance energies are reported.     

链烷的物理化学性质及其分子参数的相关性研究

用N，N'，P，q,n等分子参数表征链烷的分子大小、取代参量和相邻取代基的 相互作用，并以其为独立参量，通过回归方法建立模型来预测链烷的某些物理化学 性质，对1-9个碳原子链烷的原子化焓、标准生成焓、汽化焓等理化性质的预测表 明该模型的原理简单、方法实用、结果可靠。其预测值民实验值吻合良好，且置信 度高达99.5%。     

NMR investigation of the interaction of vanadate with carbasilatranes in aqueous solutions

Reaction of vanadate with carbasilatranes [methoxy{N,N',N' '-2,2',3-[bis(1-methylethanolato)(propyl)]amino}silane (1), methoxy{N,N',N' '-2,2',3-[bis(1-ethanolethanolato)(propyl)]amino}silane (2), and {N,N',N' '-2,2',2-[bis(ethanolato)(glycolpropyl ether)]amino}silane (3)] in aqueous solution results in the formation of vanadosilicates and five-coordinated chelate vanadium(V) complexes as evidenced by 51V, 1H, and 13C NMR spectroscopy. Chiral carbasilatrane S,S-1 was characterized in the solid state by X-ray diffraction, revealing a trigonal bipyramidal geometry around the metal ion, with one unidentate methoxy group and one atrane nitrogen atom at the axial positions and one carbon and two atrane oxygen atoms at the equatorial plane of the bipyramid. Crystal data (Mo Kalpha; 100(2) K) are as follows: orthorhombic space group P2(1)2(1)2(1); a = 8.8751(6), b = 9.7031(7), c = 14.2263(12) A; Z = 4. The complexation of vanadium either with 1 or 2 is stereoselective yielding approximately 94% of the complex containing ligand in the S,R-configuration. The lower ability of the S,S- and R,R-diastereoisomers of 1 and 2 to ligate vanadate was attributed to stereochemical factors, dictating a square pyramidal geometry for the chelated complexes. A dynamic process between the vanadium chelate complexes and the respective carbasilatranes was evaluated by 2D {1H} EXSY NMR spectroscopy. These spectra show that the vanadate complexes with the open carbasilatranes exchange more slowly with the free ligand compared to the respective alcohol aminate complexes.     

Uranyl complexes of alpha-carboxypolymethylenediaminetetra-acetic acids

The uranyl complexes of N,N,N',N'-tetrakis(carboxymethyl)-2,3-diaminopropionic acid, N,N,N',N'-tetrakis(carboxymethyl)diaminobutyric acid, N,N,N',N'-tetrakis(carboxymethyl)ornithine and N,N,N',N'-tetrakiscarboxymethyl)lysine have been studied by potentiometry, with computer evaluation of the titration data by the MINIQUAD program. Stability constants of the 1:1 and 2:1 metal:ligand chelates have been determined as well as the hydrolysis and polymerization constants at 25 degrees in 0.1M potassium nitrate. Results are compared with those obtained for the uranyl complexes of the corresponding members of the series of the polymethylenediaminetetra-acetic acids.     

Synthesis and characterization of new cationic hexacoordinate silanes

The reaction of N,N,N',N"-pentamethyldiethylenetriamine (pmdeta) with HSiCl3 and H2SiCl2 in dry CH2Cl2 affords the novel cationic intermolecular hexacoordinate silanes [pmdeta.HSiCl2]+Cl- (1) and [pmdeta.H2SiCl]+Cl(2), respectively. The addition of N,N,N',N',N"-pentaethyldiethylenetriamine (pedeta) to a solution of HSiCl3 in dry CH2Cl2 gives the redistribution product formulated as the salt [pedeta.H2SiCl]+Cl- (3) and SiC4. Treatment of H2SiCl2 with pedeta and N,N,N',N',N",N"'-hexamethyltriethylenetetramine (hmteta) produces [pedeta.H2SiCl]+Cl(3) and [hmteta.H2SiCl]+C1- (HCl) (4). In 4, the fourth amine is not bonded to silicon. Reactions of 2, 3, and 4 with NaBPh4 give the ion exchange products [pmdeta.H2SiC1]+BPh4- (5), [pedeta.H2SiCl]+BPh4- (6), and [hmteta.H2SiCl]+BPh4- (HCl) (7), respectively. The salts 1, 5, 6, and 7 were characterized by single-crystal X-ray diffraction analysis. Most notable is that the cations in 1, 5, 6, and 7 are slightly distorted octahedra in which two hydrogen atoms are at the trans positions. The reactions of 3 with tmeda and pmdeta afford the intermolecular ligand exchange products tmeda.H2SiCl2 and 2, respectively.     

Electronic coupling in tetraanisylarylenediamine mixed-valence systems: the interplay between bridge energy and geometric factors

We have investigated three organic mixed-valence systems that possess nearly identical inter-redox site distances and differ by the nature of the bridging units benzene, naphthalene, and anthracene: the N,N,N',N'-tetra(4-methoxyphenyl)-1,4-phenylenene-diamine radical cation (1+), the 1,4-bis(N,N-di(4-methoxyphenyl)-amino)naphthalene radical cation (2+), and the 9,10-bis(N,N-di(4-methoxyphenyl)amino)anthracene radical cation (3+). The electronic interactions in these systems have been studied by means of gas-phase ultraviolet photoelectron spectroscopy, vis/NIR spectroscopy, and electronic-structure calculations. The experimental and theoretical results concur to indicate that the strength of electronic interaction decreases in the following order of bridging units: benzene > naphthalene > anthracene. This finding contradicts the usual expectation that anthracene is superior to benzene as a driving force for electronic communication. We explain these results in terms of a super-exchange mechanism and its strong dependence on steric interactions.     

Ciprofloxacin photosensitized oxidation of 2'-deoxyguanosine-5'-monophosphate in neutral aqueous solution

Laser flash photolysis studies have been carried out to investigate the reactions of ciprofloxacin (CPX) with 2'-deoxyguanosine-5'-monophosphate (dGMP), N, N, N', N'-tetramethyl-p-phenylenediamine (TMPD) and ferulic acid (FCA) in neutral aqueous solutions, respectively. CPX triplet state ((3)CPX*) can be quenched by TMPD, FCA and dGMP, with rate constants of 1.8 × 10(9), 1.5 × 10(9) and 5.8 × 10(7) dm(3) mol(-1) s(-1), respectively. TMPD radical cation (TMPD(·+)) and FCA radical cation (FCA(·+)) were observed directly. The formation rate of CPX radical anion (CPX(·-)) was determined to be 1.5 × 10(9) dm(3) mol(-1) s(-1). Redox reaction of dGMP was investigated through competing reactions using TMPD and FCA as probe. The triplet energy of CPX was determined to be 262 kJ mol(-1). Electron transfer from TMPD, FCA and dGMP to (3)CPX* was proposed.     

Thermolyses of O-phenyl oxime ethers. A new source of iminyl radicals and a new source of aryloxyl radicals

Six O-phenyl ketoxime ethers, RR'C=NOPh 1-6, with RR' = diaryl, dialkyl, and arylalkyl, together with N-phenoxybenzimidic acid phenyl ether, PhO(Ph)C=NOPh, 7, have been shown to thermolyze at moderate temperatures with "clean" N-O bond homolyses to yield iminyl and phenoxyl radicals, RR'C=N(*) and PhO(*). Since 1-6 can be synthesized at room temperature, these compounds provide a new and potentially useful source of iminyls for syntheses. The iminyl from 7 undergoes a competition between beta-scission, to PhCN and PhO(*), and cyclization to an oxazole. Rate constants, 10(6) k/s(-1), at 90 degrees C for 1-6 range from 4.2 (RR' = 9-fluorenyl) to 180 (RR' = 9-bicyclononanyl), and that for 7 is 0.61. The estimated activation enthalpies for N-O bond scission are in satisfactory agreement with the results of DFT calculations of N-O bond dissociation enthalpies, BDEs, and represent the first thermochemical data for any reaction yielding iminyl radicals. The small range in k (N-O homolyses) is consistent with the known sigma structure of these radicals, and the variations in k and N-O BDEs with changes in RR' are rationalized in terms of iminyl radical stabilization by hyperconjugation: RR'C=N(*) <--> R(*)R'C[triple bond]N. Calculated N-H BDEs in the corresponding RR'C=NH are also presented.     

Consequences of correlated solvation on the structures and reactivities of RLi-diamine complexes: 1,2-addition and alpha-lithiation reactions of imines by TMEDA-solvated n-butyllithium and phenyllithium.

6Li and (13)C NMR spectroscopic studies were carried out on [(6)Li]n-BuLi and [(6)Li]PhLi (RLi) in toluene-d(8) containing the following diamines: N,N,N',N'-tetramethylethylenediamine (TMEDA), N,N,N',N'-tetraethylethylenediamine, 1,2-dipyrrolidinoethane, 1,2-dipiperidinoethane, N,N,N',N'-tetramethylpropanediamine, trans-(R,R)-N,N,N',N'-tetramethylcyclohexanediamine, and (-)-sparteine. Dimers of general structure (RLi)(2)S(2) (S = chelating diamine) are formed in each case. Treatment of RLi with two different diamines (S and S') affords homosolvates (RLi)(2)S(2) and (RLi)(2)S'(2) along with a heterosolvate (RLi)(2)SS'. Relative binding constants and associated free energies for the sequential solvent substitutions are obtained by competing pairs of diamines. The high relative stabilities of certain heterosolvates indicate that solvent binding to the RLi dimer can be highly correlated. Rate studies of both the 1,2-addition of RLi/TMEDA to the N-isopropylimine of cyclohexane carboxaldehyde and the RLi/TMEDA-mediated alpha-lithiation of the N-isopropylimine of cyclohexanone reveal monomer-based transition structures, [(RLi)(TMEDA)(imine)], in all cases. The complex relationships of solvent binding constants and relative reactivities toward 1,2-additions and alpha-lithiations are discussed.     

Mono-, di-, and tricoordinated phosphorus attached to a N-N unit: an experimental and theoretical study

N,N',N'-[Tris(trimethylsilyl)]hydrazino-diphenylphosphane, (TMS)2 N-(TMS)N-PPh2 (1), and N,N',N'-[tris(trimethylsilyl)]hydrazino-phenyl(chloro)phosphane, (TMS)2 N-(TMS)N-P(Cl)Ph2 (2), were obtained in the reaction of bis-[lithium-tris(trimethylsilyl)hydrazide] with Ph(n)PCl(3 - n) (n = 1, 2). The structure and bonding of both species are discussed on the basis of experimentally observed (X-ray, Raman, NMR, and MS) and theoretically obtained data (B3LYP/6-31G(d,p), NBO analysis). Oxidation with sulfur and selenium results in the formation of (TMS)2 N-(TMS)N-P(S)Ph2 (4), (TMS)2 N-(TMS)N-P(Se)Ph2 (5), (TMS)2 N-(TMS)N-P(S)Ph(Cl) (6), and (TMS)2 N-(TMS)N-P(Se)Ph(Cl) (7). Moreover, the thermal decomposition of N,N',N'-[tris(trimethylsilyl)]hydrazine-dichlorophosphane, (TMS)2 N-(TMS)N-PCl2 (3) and the reaction with magnesium have been investigated. The formation and molecular structure of the novel MgCl2(THF)2 x 2Mg[(TMS)NP(O)2 N(TMS)2](THF) (8) salt containing the hitherto unknown (TMS)NP(O)2 N(TMS)2(2-) anion are discussed. DFT calculations (B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d,p)) are used to evaluate the bonding, ground-state structures, and energy landscape for the different isomers of 3: the thermodynamics and kinetics of the successive elimination of chlorotrimethylsilane (TMS-Cl) resulting in the formation of covalent azide analogues such as TMS-PNN or TMS-NNP.     

The intramolecular rearrangement of phosphinohydrazides [R'2P-NR-NR-M] → [RN═PR'2-NR-M]: general rules and exceptions. transformations of bulky phosphinohydrazines (R-NH-N(PPh2)2, R = tBu, Ph2P)

Reactions of diphosphinohydrazines R-NH-N(PPh(2))(2) (R = tBu (1), Ph(2)P (3)) with some metalation reagents (Co[N(SiMe(3))(2)](2), LiN(SiMe(3))(2), La[N(SiMe(3))(2)](3), nBuLi, MeLi) were performed. Compound 1 was synthesized by the reaction of Ph(2)PCl with tert-butylhydrazine hydrochloride in 83% yield. This compound reveals temperature-dependent (31)P NMR spectra due to hindered rotation about the P-N bonds. Complicated redox reaction of 1 with Co[N(SiMe(3))(2)](2) proceeds with cleavage of the P-N and N-N bonds to form a binuclear cobalt complex [Co{HN(PPh(2))(2)-κ(2)P,P'}(2)(μ-PPh(2))](2) (2) demonstrating a short Co···Co distance of 2.3857(5) ?, which implies a formal double bond between the Co atoms. Strong nucleophiles (nBuLi, MeLi) cause fragmentation of the molecules 1 and 3, while reactions of 3 with lithium and lanthanum silylamides give products of the NNP → NPN rearrangement [Li{Ph(2)P(NPPh(2))(2)-κ(2)N,N'}(THF)(2)] (4) and [La{Ph(2)P(NPPh(2))(2)-κ(2)N,N'}{N(SiMe(3))(2)}(2)] (5), respectively. These complexes represent the first examples of a κ(2)N,N' bonding mode for the triphosphazenide ligand [(Ph(2)PN)(2)PPh(2)](-). DFT calculations showed large energy gain (52.1 kcal/mol) of the [NNP](-) to [NPN](-) anion rearrangement.     

Chemical reduction of 2,4,6-tricyano-1,3,5-triazine and 1,3,5-tricyanobenzene. Formation of novel 4,4',6,6'-Tetracyano-2,2'-bitriazine and its radical anion

Chemical reduction of 2,4,6-tricyano-1,3,5-triazine, TCT, results in the formation of an unstable radical anion that undergoes immediate dimerization at a ring carbon to form [C(12)N(12)](2-), [TCT](2)(2-), characterized by a long 1.570 (4) A central C[bond]C. [TCT](2)(2-) can decompose into the radical anion of 4,4',6,6'-tetracyano-2,2'-bitriazine, [TCBT]*-, the one-electron reduced form of planar (D(2h)) TCBT, which is also structurally characterized as the [TMPD][TCBT] charge-transfer complex (TMPD = N,N,N',N'-tetramethyl-p-phenylenediamine) with a 1.492 (2) A central sp(2)[bond]sp(2) C[bond]C. Although crystals could not be obtained for the radical anion [TCBT]*-, the electrochemistry (E degrees = +0.03 V), EPR (g = 2.003, (2)A((14)N) = 3.347 G, and (4)A((14)N) = 0.765 G and a line width of 0.24 G), and theoretical calculations support the formation of [TCBT]*-. In addition, thermolysis of [TCT](2)(2-) yields [TCBT]*-. Chemical reduction of 2,4,6-tricyanobenzene, TCB, forms an unstable radical anion that immediately undergoes dimerization at a ring carbon to form [C(12)H(6)N(6)](2-), [TCB](2)(2-), which has a long 1.560 (5) A central C[bond]C. Reaction of TCT with tetrathiafulvalene (TTF) forms structurally characterized [TTF][TCT], and in the presence of water, TCT hydrolyzes to 2,4-dicyano-6-hydroxy-s-triazine, DCTOH. In contrast, the reaction of TCT with TMPD forms [TMPD][TCT], which in the presence of water forms structurally characterized [HTMPD](+)[DCTO](-).     

Energetics of hydroxybenzoic acids and of the corresponding carboxyphenoxyl radicals. Intramolecular hydrogen bonding in 2-hydroxybenzoic acid

The energetics of the phenolic O-H bond in the three hydroxybenzoic acid isomers and of the intramolecular hydrogen O-H- - -O-C bond in 2-hydroxybenzoic acid, 2-OHBA, were investigated by using a combination of experimental and theoretical methods. The standard molar enthalpies of formation of monoclinic 3- and 4-hydroxybenzoic acids, at 298.15 K, were determined as Delta(f)(3-OHBA, cr) = -593.9 +/- 2.0 kJ x mol(-1) and Delta(f)(4-OHBA, cr) = -597.2 +/- 1.4 kJ x mol(-1), by combustion calorimetry. Calvet drop-sublimation calorimetric measurements on monoclinic samples of 2-, 3-, and 4-OHBA, led to the following enthalpy of sublimation values at 298.15 K: Delta(sub)(2-OHBA) = 94.4 +/- 0.4 kJ x mol(-1), Delta(sub)(3-OHBA) = 118.3 +/- 1.1 kJ x mol(-1), and Delta(sub)(4-OHBA) = 117.0 +/- 0.5 kJ x mol(-1). From the obtained Delta(f)(cr) and Delta(sub) values and the previously reported enthalpy of formation of monoclinic 2-OHBA (-591.7 +/- 1.3 kJ x mol(-1)), it was possible to derive Delta(f)(2-OHBA, g) = -497.3 +/- 1.4 kJ x mol(-1), Delta(f)(3-OHBA, g) = -475.6 +/- 2.3 kJ x mol(-1), and Delta(f)(4-OHBA, cr) = -480.2 +/- 1.5 kJ x mol(-1). These values, together with the enthalpies of isodesmic and isogyric gas-phase reactions predicted by density functional theory (B3PW91/aug-cc-pVDZ, MPW1PW91/aug-cc-pVDZ, and MPW1PW91/aug-cc-pVTZ) and the CBS-QMPW1 methods, were used to derive the enthalpies of formation of the gaseous 2-, 3-, and 4-carboxyphenoxyl radicals as (2-HOOCC(6)H(4)O(*), g) = -322.5 +/- 3.0 kJ.mol(-1) Delta(f)(3-HOOCC(6)H(4)O(*), g) = -310.0 +/- 3.0 kJ x mol(-1), and Delta(f)(4-HOOCC(6)H(4)O(*), g) = -318.2 +/- 3.0 kJ x mol(-1). The O-H bond dissociation enthalpies in 2-OHBA, 3-OHBA, and 4-OHBA were 392.8 +/- 3.3, 383.6 +/- 3.8, and 380.0 +/- 3.4 kJ x mol(-1), respectively. Finally, by using the ortho-para method, it was found that the H- - -O intramolecular hydrogen bond in the 2-carboxyphenoxyl radical is 25.7 kJ x mol(-1), which is ca. 6-9 kJ x mol(-1) above the one estimated in its parent (2-OHBA), viz. 20.2 kJ x mol(-1) (theoretical) or 17.1 +/- 2.1 kJ x mol(-1) (experimental).     

含酚氧桥的新型Cu(Ⅱ)-Mn(Ⅱ)和Cu(Ⅱ)-Co(Ⅱ)配合物的合成和磁性

合成了3种新型配合物[Cu(samen)Mn(NO_(2-)Phen)_2](1)、[Cu(sampn)Mn(NO_(2-)Phen)_2](2)和[Cu(samen)CO(terp)](3)(samen~(4-)、sampn~(4-)、NO_(2-)Phen和terp分别表示N,N′-乙二水杨酰胺根阴离子、N,N′-1,2-丙二水杨酰胺根阴离子、5-硝基-1,10-菲绕啉和联三吡啶),测得配合物的变温磁化率,求出交换积分,J分别为-63cm~(-1)(1)、—65cm~(-1)(2)和—7.68cm~(-1)(3),表明金属离子间有反铁磁超交换作用。     

Reaction of HO* with guanine derivatives in aqueous solution: formation of two different redox-active OH-adduct radicals and their unimolecular transformation reactions. Properties of G(-H)*

The reaction of *OH with 2'-deoxyguanosine yields two transient species, both identified as OH adducts (G*-OH), with strongly different reactivity towards O2, or other oxidants, or to reductants. One of these, identified as the OH adduct at the C-8 position (yield 17% relative to *OH), reacts with oxygen with k=4 x 10(9)M(-1)s(-1); in the absence of oxygen it undergoes a rapid ring-opening reaction (k = 2 x 10(5) s(-1) at pH4-9), visible as an increase of absorbance at 300-310 nm. This OH adduct and its ring-opened successor are one-electron reductants towards, for example, methylviologen or [Fe(III)(CN)6]3-. The second adduct, identified as the OH adduct at the 4-position (yield of 60-70% relative to *OH), has oxidizing properties (towards N,N,N',N'-tetra-methyl-p-phenylenediamine, promethazine, or [Fe(II)(CN)6]4-). This OH adduct undergoes a slower transformation reaction (k = 6 x 10(3) s(-1) in neutral, unbuffered solution) to produce the even more strongly oxidizing (deprotonated, depending on pH) 2'-deoxyguanosine radical cation, and it practically does not react with oxygen (k< or = 10(6)M(-1)s(-1)). The (deprotonated) radical cation, in dilute aqueous solution, does not give rise to 8-oxoguanosine as a product. However, it is able to react with ribose with k< or =4 x 10(3)M(-1)S(-1).     

Pentamethylcyclopentadienyl-iridium(III) complexes with pyridylamino ligands: synthesis and applications as asymmetric catalysts for Diels-Alder reactions

Reaction of the dimer [(Cp*IrCl)2(P-Cl)2] with chiral pyridylamino ligands (pyam, L1-L5) in the presence of NaSbF6 gave complexes [Cp*IrCl(pyam)][SbF6] 1-5 as diastereomeric mixtures, which have been fully characterised, including the X-ray molecular structure determination of the complexes (S(Ir),R(N),R(C))-[Cp*IrClL1][SbF6] 1a and (R(Ir),S(N),S(C))-[Cp*IrClL5][SbF6] 5a. Treatment of these cations with AgSbF6 affords the corresponding aqua species [Cp*Ir(pyam)(H2O)][SbF6]2 6-10 which have been also fully characterised. The molecular structure of the complex (S(Ir),R(N),R(C))-[Cp*IrL,(H2O)][SbF6]2 6 has been determined by X-ray diffractometric methods. The aqua complexes [Cp*Ir(pyam)(H2O)][SbF6]2 (6, pyam = L2 (7), L3 (8)) evolve to the cyclometallated species [Cp*Ir{kappa3(N,N',C)-(R)-(C6H4)CH(CH3)NHCH2C5NH4}][SbF6] (11), [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)-NHCH2C5NH4)}][SbF6] (12), and [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)NHCH2C9NH6)}][SbF6] (13) respectively, via intramolecular activation of an ortho C-H aryl bond. Complexes 6-10 are enantioselective catalysts for the Diels-Alder reaction between methacrolein and cyclopentadiene. Reaction occurs rapidly at room temperature with good exo : endo selectivity (from 81 : 19 to 98 : 2) and moderate enantioselectivity (up to 72%). The involved intermediate Lewis acid-dienophile compounds [Cp*Ir(pyam)(methacrolein)][SbF]2 (pyam = L4 (14), L5 (15)) have been isolated and characterised.     

两个手性Salen型过渡金属配合物的合成、波谱与结构

本文报道了2个手性Salen型过渡金属配合物[(N,N′-bis(3-t-butyl-5-methylsalicylidene)-1S,2S-cyclohexanediamine-N,N′,O,O′) nickel(Ⅱ)] (1)和[(N,N′-bis(3-t-butyl-5-methylsalicylidene)-1S,2S-cyclohexanediamine-N,N′,O,O′) copper(Ⅱ)] (2)的合成、波谱与结构表征。它们由(1S,2S)-环己烷-1,2-二胺和3-叔丁基-5-甲基-2-羟基苯甲醛发生席夫碱缩合反应制得的配体分别与Cu(Ⅱ)和Ni(Ⅱ)盐反应而得到。产品经过红外光谱、元素分析、电喷雾质谱、紫外和圆二色光谱等方法表征,并测定其晶体结构。结果表明配合物1和2中的中心金属离子Cu(Ⅱ)和Ni(Ⅱ)均为四配位平面正方形配位构型,而且在其晶体堆积中观察到一种通过芳环之间弱π-π相互作用形成的二聚结构。     

二次配体结构和[CuCl4]2－构型对层间隧道结构的影响研究

设计合成的质子配体, N,N,N’,N’-四(对甲基苄基)乙二胺(SL1)和N,N,N’,N’-四苄基乙二胺(SL2), 是连有大体积取代基团的含N双齿配体, 它可通过二次球形配位, 与第一络合物[CuCl4]2－形成层间隧道框架结构. 环戊醇分子和乙醇分子分别被填入由SL1和SL2构筑的隧道中, 形成包结化合物. 晶体结构分析结果表明, 这样的配体易于与指导基团通过NH＋…Cl－氢键作用进行双齿配位并形成1D带和2D层结构; SL1 2D层间的苄基呈平行堆砌, 形成1D亲水性隧道框架, SL2 2D层间的苄基呈交错堆砌, 形成了1D疏水性隧道框架. 实验结果表明, 层间隧道框架结构的孔径及极性与第二配体的分子长度、指导基团的构型以及客体分子的形状大小有关.