Direct determination of the complete set of iron normal modes in a porphyrin-imidazole model for carbonmonoxy-heme proteins: [Fe(TPP)(CO)(1-MeIm)

Detailed Fe vibrational spectra have been obtained for the heme model complex [Fe(TPP)(CO)(1-MeIm)] using a new, highly selective and quantitative technique, Nuclear Resonance Vibrational Spectroscopy (NRVS). This spectroscopy measures the complete vibrational density of states for iron atoms, from which normal modes can be calculated via refinement of the force constants. These data and mode assignments can reveal previously undetected vibrations and are useful for validating predictions based on optical spectroscopies and density functional theory, for example. Vibrational modes of the iron porphyrin-imidazole compound [Fe(TPP)(CO)(1-MeIm)] have been determined by refining normal mode calculations to NRVS data obtained at an X-ray synchrotron source. Iron dynamics of this compound, which serves as a useful model for the active site in the six-coordinate heme protein, carbonmonoxy-myoglobin, are discussed in relation to recently determined dynamics of a five-coordinate deoxy-myoglobin model, [Fe(TPP)(2-MeHIm)]. For the first time in a six-coordinate heme system, the iron-imidazole stretch mode has been observed, at 226 cm(-)(1). The heme in-plane modes with large contributions from the nu(42), nu(49), nu(50), and nu(53) modes of the core porphyrin are identified. In general, the iron modes can be attributed to coupling with the porphyrin core, the CO ligand, the imidazole ring, and/or the phenyl rings. Other significant findings are the observation that the porphyrin ring peripheral substituents are strongly coupled to the iron doming mode and that the Fe-C-O tilting and bending modes are related by a negative interaction force constant.     

Detailed assignment of the magnetic circular dichroism and UV-vis spectra of five-coordinate high-spin ferric [Fe(TPP)(Cl)

High-spin (hs) ferric heme centers occur in the catalytic or redox cycles of many metalloproteins and exhibit very complicated magnetic circular dichroism (MCD) and UV-vis absorption spectra. Therefore, detailed assignments of the MCD spectra of these species are missing. In this study, the electronic spectra (MCD and UV-vis) of the five-coordinate hs ferric model complex [Fe(TPP)(Cl)] are analyzed and assigned for the first time. A correlated fit of the absorption and low-temperature MCD spectra of [Fe(TPP)(Cl)] lead to the identification of at least 20 different electronic transitions. The assignments of these spectra are based on the following: (a) variable temperature and variable field saturation data, (b) time-dependent density functional theory calculations, (c) MCD pseudo A-terms, and (d) correlation to resonance Raman (rRaman) data to validate the assignments. From these results, a number of puzzling questions about the electronic spectra of [Fe(TPP)(Cl)] are answered. The Soret band in [Fe(TPP)(Cl)] is split into three components because one of its components is mixed with the porphyrin A2u72-->Eg82/83 (pi-->pi*) transition. The broad, intense absorption feature at higher energy from the Soret band is due to one of the Soret components and a mixed sigma and pi chloro to iron CT transition. The high-temperature MCD data allow for the identification of the Q v band at 20 202 cm(-1), which corresponds to the C-term feature at 20 150 cm(-1). Q is not observed but can be localized by correlation to rRaman data published before. Finally, the low energy absorption band around 650 nm is assigned to two P-->Fe charge transfer transitions, one being the long sought after A1u(HOMO)-->d pi transition.     

Low-spin ferriheme models of the cytochromes: correlation of molecular structure with EPR spectral type

The preparation and characterization of the following bis-imidazole and bis-pyridine complexes of octamethyltetraphenylporphyrinatoiron(III), Fe(III)OMTPP, octaethyltetraphenylporphyrinatoiron(III), Fe(III)OETPP, and tetra-beta,beta'-tetramethylenetetraphenylporphyrinatoiron(III), Fe(III)TC(6)TPP, are reported: paral-[FeOMTPP(1-MeIm)(2)]Cl, perp-[FeOMTPP(1-MeIm)(2)]Cl, [FeOETPP(1-MeIm)(2)]Cl, [FeTC(6)TPP(1-MeIm)(2)]Cl, [FeOMTPP(4-Me(2)NPy)(2)]Cl, and [FeOMTPP(2-MeHIm)(2)]Cl. Crystal structure analysis shows that paral-[FeOMTPP(1-MeIm)(2)]Cl has its axial ligands in close to parallel orientation (the actual dihedral angle between the planes of the imidazole ligands is 19.5 degrees ), while perp-[FeOMTPP(1-MeIm)(2)]Cl has the axial imidazole ligand planes oriented at 90 degrees to each other and 29 degrees away from the closest N(P)-Fe-N(P) axis. [FeOETPP(1-MeIm)(2)]Cl has its axial ligands close to perpendicular orientation (the actual dihedral angle between the planes of the imidazole ligands is 73.1 degrees ). In all three cases the porphyrin core adopts relatively purely saddled geometry. The [FeTC(6)TPP(1-MeIm)(2)]Cl complex is the most planar and has the highest contribution of a ruffled component in the overall saddled structure compared to all other complexes in this study. The estimated numerical contribution of saddled and ruffled components is 0.68:0.32, respectively. Axial ligand planes are perpendicular to each other and 15.3 degrees away from the closest N(P)-Fe-N(P) axis. The Fe-N(P) bond is the longest in the series of octaalkyltetraphenylporphyrinatoiron(III) complexes due to [FeTC(6)TPP(1-MeIm)(2)]Cl having the least distorted porphyrin core. In addition to these three complexes, two crystalline forms each of [FeOMTPP(4-Me(2)NPy)(2)]Cl and [FeOMTPP(2-MeHIm)(2)]Cl were obtained. In all four of these cases the axial planes are in nearly perpendicular planes in spite of quite different geometries of the porphyrin cores (from purely saddled to saddled with 30% ruffling). The EPR spectral type correlates with the geometry of the OMTPP, OETPP and TC(6)TPP complexes. For the paral-[FeOMTPP(1-MeIm)(2)]Cl, a rhombic signal with g(1) = 1.54, g(2) = 2.51, and g(3) = 2.71 is consistent with nearly parallel axial ligand orientation. For all other complexes of this study, "large g(max)" signals are observed (g(max) = 3.61 - 3.27), as are observed for nearly perpendicular ligand plane arrangement. On the basis of this and previous work, the change from "large g(max)" to normal rhombic EPR signal occurs between axial ligand plane dihedral angles of 70 degrees and 30 degrees.     

Remote effects of axial ligand substitution in heterometallic Cr≡Cr···M chains

The heterometallic complexes CrCrM(dpa)(4)Cl(2) (dpa = 2,2'-dipyridylamide) featuring linear Cl-Cr≡Cr···M-Cl chains can regiospecifically be modified via axial ligand substitution to yield OTf-Cr≡Cr···M-Cl chains (OTf = triflate) with M being Fe, Mn, or Co. The effect of OTf substitution on the Cr side of the molecule has an unusual and profound structural impact on the square-pyramidal transition metal M. Specifically, elongation of the four equatorial M-N(py) bonds and the axial M-Cl bonds by 0.03 and 0.09 ? for Fe and 0.07 and 0.11 ? for Mn is observed. The longer M-Cl and M-N(py) bonds result from subtle interactions between the equatorial dpa ligand and the three metal ions. The equatorial dpa ligand responds to the introduction of the more labile OTf ligand at Cr by binding more strongly to this Cr ion which in turn weakens bonding to M. The ligand field experienced by M can be tuned by changing the Cr axial ligand, and this effect is observed in electrochemical measurements of the iron compounds.     

四-(对-十二酰氧基)苯基卟啉过渡金属配合物的合成及其液晶行为研究

合成了5,10,15,20-四-(对-十二酰氧基)苯基卟啉(简称TLPPH₂)及其Mn(Ⅲ),Fe(Ⅲ),Co(Ⅱ),Ni(Ⅱ),Cu(Ⅱ)和Zn(Ⅱ)配合物,通过元素分析、紫外可见光谱、红外光声光谱、核磁共振氢谱和摩尔电导等分析方法表征了它们的组成和结构.用DSC和偏光显微镜研究了配体及其锌配合物的液晶行为.结果表明,锌配合物的液晶相变温度始于-50.67℃,相区宽度达143℃.     

Structural, NMR, and EPR studies of S = (1)/(2) and S = (3)/(2) Fe(III) bis(4-cyanopyridine) complexes of dodecasubstituted porphyrins

The NMR and EPR spectra for three complexes, iron(III) octamethyltetraphenylporphyrin bis(4-cyanopyridine) perchlorate, [FeOMTPP(4-CNPy)(2)]ClO(4), and its octaethyl- and tetra-beta,beta'-tetramethylenetetraphenylporphyrin analogues, [FeOETPP(4-CNPy)(2)]ClO(4) and [FeTC(6)TPP(4-CNPy)(2)]ClO(4), are presented. The crystal structures of two different forms of [FeOETPP(4-CNPy)(2)]ClO(4) and one form of [FeOMTPP(4-CNPy)(2)]ClO(4) are also reported. Attempts to crystallize [FeTC(6)TPP(4-CNPy)(2)]ClO(4) were not successful. The crystal structure of [FeOMTPP(4-CNPy)(2)]ClO(4) reveals a saddled porphyrin core, a small dihedral angle between the axial ligand planes, 64.3 degrees, and an unusually large tilt angle (24.4 degrees ) of one of the axial 4-cyanopyridine ligands with respect to the normal to the porphyrin mean plane. There are 4 and 2 independent molecules in the asymmetric units of [FeOETPP(4-CNPy)(2)]ClO(4) crystallized from CD(2)Cl(2)/dodecane (1-4) and CDCl(3)/cyclohexane (5-6), respectively. The geometries of the porphyrin cores in 1-6 vary from purely saddled to saddled with 15% ruffling admixture. In all structures, the Fe-N(p) distances (1.958-1.976 A) are very short due to strong nonplanar distortion of the porphyrin cores, while the Fe-N(ax) distances are relatively long ( approximately 2.2 A) compared to the same distances in S = (1)/(2) bis(pyridine)iron(III) porphyrin complexes. An axial EPR signal is observed (g( perpendicular ) = 2.49, g( parallel ) = 1.6) in frozen solutions of both [FeOMTPP(4-CNPy)(2)]ClO(4) and [FeTC(6)TPP(4-CNPy)(2)]ClO(4) at 4.2 K, indicative of the low spin (LS, S = (1)/(2)), (d(yz)d(xz))(4)(d(xy))(1) electronic ground state for these two complexes. In agreement with a recent publication (Ikeue, T.; Ohgo, Y.; Ongayi, O.; Vicente, M. G. H.; Nakamura, M. Inorg. Chem. 2003, 42, 5560-5571), the EPR spectra of [FeOETPP(4-CNPy)(2)]ClO(4) are typical of the S = (3)/(2) state, with g values of 5.21, 4.25, and 2.07. A small amount of LS species with g = 3.03 is also present. However, distinct from previous conclusions, large negative phenyl-H shift differences delta(m) - delta(o) and delta(m) - delta(p) in the (1)H NMR spectra indicate significant negative spin density at the meso-carbons, and the larger than expected positive average CH(2) shifts are also consistent with a significant population of the S = 2 Fe(II), S = (1)/(2) porphyrin pi-cation radical state, with antiferromagnetic coupling between the metal and porphyrin unpaired electrons. This is the first example of this type of porphyrin-to-metal electron transfer to produce a partial or complete porphyrinate radical state, with antiferromagnetic coupling between metal and macrocycle unpaired electrons in an iron porphyrinate. The kinetics of ring inversion were studied for the [FeOETPP(4-CNPy)(2)]ClO(4) complex using NOESY/EXSY techniques and for the [FeTC(6)TPP(4-CNPy)(2)]ClO(4) complex using DNMR techniques. For the former, the free energy of activation, deltaG, and rate of ring inversion in CD(2)Cl(2) extrapolated to 298 K are 63(2) kJ mol(-)(1) and 59 s(-)(1), respectively, while for the latter the rate of ring inversion at 298 K is at least 4.4 x 10(7) s(-)(1), which attests to the much greater flexibility of the TC(6)TPP ring. The NMR and EPR data are consistent with solution magnetic susceptibility measurements that show S = (3)/(2) in the temperature range from 320 to 180 K for [FeOETPP(4-CNPy)(2)](+), while both [FeOMTPP(4-CNPy)(2)](+) and [FeTC(6)TPP(4-CNPy)(2)](+) change their spin state from S = (3)/(2) at room temperature to mainly LS (S = (1)/(2)) upon cooling to 180 K.     

Crystallographic identification of a series of manganese porphyrin complexes with nitrogenous bases

Studying the axial ligation behavior of metalloporphyrins with nitrogenous bases helps to better understand not only the biological function of heme‐based protein systems, but also the catalytic properties of porphyrin‐based reaction sites in other biomimetic synthetic support environments. Unlike iron porphyrin complexes, little is known about the axial ligation behavior of Mn porphyrins, particularly in the solid state with Mn in the +3 oxidation state. Here, we present the syntheses and crystal and molecular structures of three new high‐spin manganese(III) porphyrin complexes with the different amine‐based axial ligands imidazole (im), piperidine (pip), and 1,4‐diazabicyclo[2.2.2]octane (DABCO), namely bis(imidazole)(5,10,15,20‐tetraphenylporphyrinato)manganese(III) chloride chloroform disolvate, [Mn(C₄₄H₂₈N₄)(C₃H₄N₂)₂]Cl·2CHCl₃ or [Mn(TPP)(im)₂]Cl·2CHCl₃ (TPP = 5,10,15,20‐tetraphenylporphyrin), (I), bis(piperidine)(5,10,15,20‐tetraphenylporphyrinato)manganese(III) chloride, [Mn(C₄₄H₂₈N₄)(C₅H₁₁N)₂]Cl or [Mn(TPP)(pip)₂]Cl, (II), and chlorido(1,4‐diazabicyclo[2.2.2]octane)(5,10,15,20‐tetraphenylporphyrin)manganese(III)–1,4‐diazabicyclo[2.2.2]octane–toluene–water (4/4/4/1), [Mn(C₄₄H₂₈N₄)Cl(C₆H₁₂N₂)]·C₆H₁₂N₂·C₇H₈·0.25H₂O or [Mn(TPP)Cl(DABCO)]·(DABCO)·(toluene)·0.25H₂O, (IV). A fourth complex, chlorido(pyridine)(5,10,15,20‐tetraphenylporphryinato)manganese(III) pyridine disolvate, [Mn(C₄₄H₂₈N₄)Cl(C₅H₅N)]·2C₅H₅N or [Mn(TPP)Cl(py)]·2(py), (III), acquired using different crystallization methods from published data, is also reported and compared to the previous structures.     

四(对-十八酰氧基)苯基卟啉及其过渡金属配合物的合成及红外光声光谱研究

合成了5,10,15,20-四(对-十八酰氧基)苯基卟啉及其Mn(Ⅲ),Fe(Ⅲ),Co(Ⅱ),Ni(Ⅱ),Cu(Ⅱ)和Zn(Ⅱ)配合物,用元素分析和紫外-可见光谱等方法进行了表征.研究了这7种卟啉化合物在3600～190cm^-1范围内的傅里叶变换红外光声光谱,对主要谱带进行了经验归属.结果表明,3318.0及968.4cm^-1处的吸收谱带分别是四(对-十八酰氧基)苯基卟啉N-H键的伸缩振动和面内弯曲振动,生成配合物后这些谱带消失.243cm^-1附近的吸收谱带是M-N键伸缩振动和卟啉环变形振动的复合振动,321cm^-1附近的吸收谱带是M-Cl键的伸缩振动,金属敏感带出现在1350,1018,995,802,740,632和232cm^-1附近.     

Laser flash photolysis generation and kinetic studies of porphyrin-manganese-oxo intermediates. Rate constants for oxidations effected by porphyrin-Mn(V)-oxo species and apparent disproportionation equilibrium constants for porphyrin-Mn(IV)-oxo species

Porphyrin-manganese(V)-oxo and porphyrin-manganese(IV)-oxo species were produced in organic solvents by laser flash photolysis (LFP) of the corresponding porphyrin-manganese(III) perchlorate and chlorate complexes, respectively, permitting direct kinetic studies. The porphyrin systems studied were 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPFPP), and 5,10,15,20-tetrakis(4-methylpyridinium)porphyrin (TMPyP). The order of reactivity for (porphyrin)Mn(V)(O) derivatives in self-decay reactions in acetonitrile and in oxidations of substrates was (TPFPP) > (TMPyP) > (TPP). Representative rate constants for reaction of (TPFPP)Mn(V)(O) in acetonitrile are k = 6.1 x 10(5) M(-1) s(-1) for cis-stilbene and k = 1.4 x 10(5) M(-1) s(-1) for diphenylmethane, and the kinetic isotope effect in oxidation of ethylbenzene and ethylbenzene-d(10) is k(H)/k(D) = 2.3. Competitive oxidation reactions conducted under catalytic conditions display approximately the same relative rate constants as were found in the LFP studies of (porphyrin)Mn(V)(O) derivatives. The apparent rate constants for reactions of (porphyrin)Mn(IV)(O) species show inverted reactivity order with (TPFPP) < (TMPyP) < (TPP) in reactions with cis-stilbene, triphenylamine, and triphenylphosphine. The inverted reactivity results because (porphyrin)Mn(IV)(O) disproportionates to (porphyrin)Mn(III)X and (porphyrin)Mn(V)(O), which is the primary oxidant, and the equilibrium constants for disproportionation of (porphyrin)Mn(IV)(O) are in the order (TPFPP) < (TMPyP) < (TPP). The fast comproportionation reaction of (TPFPP)Mn(V)(O) with (TPFPP)Mn(III)Cl to give (TPFPP)Mn(IV)(O) (k = 5 x 10(8) M(-1) s(-1)) and disproportionation reaction of (TPP)Mn(IV)(O) to give (TPP)Mn(V)(O) and (TPP)Mn(III)X (k approximately 2.5 x 10(9) M(-1) s(-1)) were observed. The relative populations of (porphyrin)Mn(V)(O) and (porphyrin)Mn(IV)(O) were determined from the ratios of observed rate constants for self-decay reactions in acetonitrile and oxidation reactions of cis-stilbene by the two oxo derivatives, and apparent disproportionation equilibrium constants for the three systems in acetonitrile were estimated. A model for oxidations under catalytic conditions is presented.     

四（对—羟基）苯基卟啉配合物的傅里叶变换红外光声光谱

四（对-羟基）苯基卟啉（H2THPP）不仅能作为分析试剂，而且有一定的抗癌活性，还可作为合成卟啉类液晶材料的中间体．这种配体及其配合物由于颜色深、透光性能差和散射较强，用普通红外光谱法开展其振动光谱研究存在一定的困难．我们在用红外光声光谱（FTIR－PAS）技术[1]成功地研究了部分过渡金属、稀土金属叶琳配合物的基础上[2，3]，测试并研究了H2THPP及其Cr（III）、Mn（III）、Fe（III）、Co（II）、Ni（II）、Cu（II）、Zn（II）配合物在3700～200cm－1范围内的FTIR－PAS．对主要谱带进行了经验归属，讨论了配…     

Density functional theory studies on the Raman and IR spectra of meso-tetraphenylporphyrin diacid

The vibrational spectra of meso-tetraphenylporphyrin diacid (H4TPP2+) have been studied with the density functional theory. Raman and IR spectra of H4TPP2+ and its N-deuterated analogue (D4TPP2+) are measured and compared with the computational results. Complete assignments of observed IR and Raman bands were proposed on the bases of calculation results. The DFT calculations reproduce 140 observed fundamentals with the RMS 8.6 cm-1. The computational as well as the experimental results reveal that the saddle-distortion of porphyrin macrocycle for the diacid leads to a significant effect on its vibrational spectra. Especially, several out-of-plane skeletal modes, which were either unobserved or very weak in the Raman spectra of CuTPP and H2TPP, are activated in the Raman spectra of the diacids. In addition, enhancement for the Raman bands of phenyl CC stretching modes were observed and attributed to the conjugation effect of pi-systems of the phenyl and the porphyrinato macrocycles.     

Chemistry of nitrosyliron complexes supported by a β-diketiminate ligand

Several nitrosyl complexes of Fe and Co have been prepared using the sterically hindered Ar-nacnac ligand (Ar-nacnac = anion of [(2,6-diisopropylphenyl)NC(Me)](2)CH). The dinitrosyliron complexes [Fe(NO)(2)(Ar-nacnac)] (1) and (Bu(4)N)[Fe(NO)(2)(Ar-nacnac)] (2) react with [Fe(III)(TPP)Cl] (TPP = tetraphenylporphine dianion) to generate [Fe(II)(NO)(TPP)] and the corresponding mononitrosyliron complexes. The factors governing NO transfer with dinitrosyliron complexes (DNICs) 1 and 2 are evaluated, together with the chemistry of the related mononitrosyliron complex, [Fe(NO)Br(Ar-nacnac)] (4). The synthesis and properties of the related cobalt dinitrosyl [Co(NO)(2)(Ar-nacnac)] (3) is also discussed for comparison to DNICs 1 and 2. The solid-state structures of several of these compounds as determined by X-ray crystallography are reported.     

Infrared spectra of metal anthranilates

The infrared spectra of the sodium salts and the Mn(II), Co(II), Ni(II), Cu(II) and Zn(Il) chelates of anthranilic acid and 5-methyl-, 5-chloro-, 5-bromo-and 5-iodo-anthranilic acid are discussed. ¹⁵N-Labelling of sodium anthranilate and the complexes of anthranilic acid provides assignments of the ligand vibrations involving the amino group. The metal-ligand stretching frequencies (vM-N and vM-O) are assigned by observing the effects on the spectra caused by ¹⁵N-labelling, metal ion substitution and ligand substitution. The vCu-O bands are split by tetragonal distortion in the Cu(II) complex which involves elongation of the axial Cu~O bonds. The metal ion dependence of vM-N and vM-O parallels the Irving-Williams stability sequence. The ligand substituents shift vM-O in accordance with their inductive effects while vM-N exhibits a substituent dependence which is roughly the opposite of that shown by vM-O.     

密闭高压法合成桥连金属四苯基卟啉多聚物

采用密闭高压法合成出一系列桥连金属四苯基卟啉多聚物[M(TPP)L]_n[M＝Fe(Ⅲ),Co(Ⅱ),Mn(Ⅱ),Cu(Ⅱ),Ni(Ⅱ);L＝吡嗪,咪唑,联吡啶].通过固体紫外反射、光电压和红外等方法予以表征.在固体紫外反射和光电压光谱中,金属卟啉聚合物的Soret带均发生了显著蓝移.在红外光谱中,单体Co(TPP)(pyz)₂在1598cm^-1处显示一个强吸收,而聚合物[Co(TPP)(pyz)]_n在1600cm^-1附近仅有极弱的吸收,单体在3482,3423,2921,2854,1004,792和611cm^-1处出现的强吸收在聚合物中接近消失,说明此聚合物与单体相比对称性增加,而单体在1644,1353和1070cm^-1处的吸收分别向高场方向位移13,25和15cm^-1.实验中还发现,对于不同中心金属离子,反应完成的时间不同,时间由短到长的顺序为:Co(Ⅱ)＞Fe(Ⅲ)＞Ni(Ⅱ)＞Cu(Ⅱ)＞Mn(Ⅲ);不同桥连配体反应完成的时间由短到长顺序是联吡啶＞吡嗪＞咪唑.     

Vibrational spectroscopic studies of metal(II) halide benzimidazole

Infrared spectra (4000–200 cm⁻¹) are reported for metal halide(II) benzimidazole complexes of the following stoichiometries: M(benz)X₂ [M=Cd, Cu; X=Cl, Br; BENZ=benzimidazole], Co(benz)₂, and Co(benz)₂X₂ [X=Cl, Br, I]. Vibrational assignments are given for all the observed bands. The analysis of the vibrational spectra indicates that there are some structure–spectra correlations. For a given series of isomorphous complexes the sum of the difference between the values of the vibrational modes of uncoordinated benzimidazole and coordinated to metal ion benzimidazole was found to increase in the order of the second ionization potentials of metals.     

Photoexcitation in Cu(I) and Re(I) complexes containing substituted dipyrido[3,2-a:2',3'-c]phenazine: a spectroscopic and density functional theoretical study

Copper(I) and rhenium(I) complexes [Cu(PPh(3))(2)(dppz-11-COOEt)]BF(4), [Cu(PPh(3))(2)(dppz-11-Br)]BF(4), [Re(CO)(3)Cl(dppz-11-COOEt)] and [Re(CO)(3)Cl(dppz-11-Br)] (dppz-11-COOEt = dipyrido-[3,2a:2',3'c]phenazine-11-carboxylic ethyl ester, dppz-11-Br = 11-bromo-dipyrido[3,2a:2',3'c]-phenazine) have been studied using Raman, resonance Raman, and transient resonance Raman (TR(2)) spectroscopy, in conjunction with computational chemistry. DFT (B3LYP) frequency calculations with a 6-31G(d) basis set for the ligands and copper(I) centers and an effective core potential (LANL2DZ) for rhenium in the rhenium(I) complexes show close agreement with the experimental nonresonance Raman spectra. Modes that are phenazine-based, phenanthroline-based, and delocalized across the entire ligand structure were identified. The nature of the absorbing chromophores at 356 nm for ligands and complexes was established using resonance Raman spectroscopy in concert with vibrational assignments from calculations. This analysis reveals that the dominant chromophore for the complexes measured at 356 nm is ligand-centered (LC), except for [Re(CO)(3)Cl(dppz-11-Br)], which appears to have additional chromophores at this wavelength. Calculations on the reduced complexes, undertaken to model the metal-to-ligand charge transfer (MLCT) excited state, show that the reducing electron occupies a ligand MO that is delocalized across the ligand structure. Resonance Raman spectra (lambda(exc) = 514.5 nm) of the reduced rhenium complexes show a similar spectral pattern to that observed in [Re(CO)(3)Cl(dppz)](*-); the measured bands are therefore attributed to ligand radical anion modes. These bands lie at 1583-1593 cm(-1) for [Re(CO)(3)Cl(dppz-11-COOEt)] and 1611 cm(-1) for [Re(CO)(3)Cl(dppz-11-Br)]. The thermally equilibrated excited states are examined using nanosecond-TR(2) spectroscopy (lambda(exc) = 354.7 nm). The TR(2) spectra of the ligands provide spectral signatures for the (3)LC state. A band at 1382 cm(-1) is identified as a marker for the (3)LC states of both ligands. TR(2) spectra of the copper and rhenium complexes of dppz-11-Br show this (3)LC band, but it is not prominent in the spectra of [Cu(PPh(3))(2)(dppz-11-COOEt)](+) and [Re(CO)(3)Cl(dppz-11-COOEt)]. Calculations suggest that the lowest triplet states of both of the rhenium(I) complexes and [Cu(PPh(3))(2)(dppz-11-Br)](+) are metal-to-ligand charge transfer in nature, but the lowest triplet state of [Cu(PPh(3))(2)(dppz-11-COOEt)](+) appears to be LC in character.     

Nuclear resonance vibrational spectra of five-coordinate imidazole-ligated iron(II) porphyrinates

Nuclear resonance vibrational spectra have been obtained for six five-coordinate imidazole-ligated iron(II) porphyrinates, [Fe(Por)(L)] (Por = tetraphenylporphyrinate, octaethylporphyrinate, tetratolylporphyrinate, or protoporphyrinate IX and L = 2-methylimidazole or 1,2-dimethylimidazole). Measurements have been made on both powder and oriented crystal samples. The spectra are dominated by strong signals around 200-300 cm(-1). Although the in-plane and out-of-plane vibrations are seriously overlapped, oriented crystal spectra allow their deconvolution. Thus, oriented crystal experimental data, along with density functional theory (DFT) calculations, enable the assignment of key vibrations in the spectra. Molecular dynamics are also discussed. The nature of the Fe-N(Im) vibrations has been elaborated further than was possible from resonance Raman studies. Our study suggests that the Fe motions are coupled with the porphyrin core and peripheral groups motions. Both peripheral groups and their conformations have significant influence on the vibrational spectra (position and shape).     

Nine non-symmetric pyrazine-pyridine imide-based complexes: reversible redox and isolation of [M(II/III)(pypzca)2](0/+) when M = Co, Fe

The non-symmetric imide ligand Hpypzca (N-(2-pyrazylcarbonyl)-2-pyridinecarboxamide) has been deliberately synthesised and used to produce nine first row transition metal complexes: [M(II)(pypzca)(2)], M = Zn, Cu, Ni, Co, Fe; [M(III)(pypzca)(2)]Y, M = Co and Y = BF(4), M = Fe and Y = ClO(4); [Cu(II)(pypzca)(H(2)O)(2)]BF(4), [Mn(II)(pypzca)(Cl)(2)]HNEt(3). These are the first deliberately prepared complexes of a non-symmetric imide ligand. X-ray crystal structures of [Cu(II)(pypzca)(2)]·H(2)O, [Co(II)(pypzca)(2)], [Co(III)(pypzca)(2)]BF(4), [Cu(II)(pypzca)(H(2)O)(2)]BF(4)·H(2)O and [Mn(II)(pypzca)Cl(2)]HNEt(3) show that each of the (pypzca)(-) ligands binds in a meridional fashion via the N(3) donors. In the first three complexes, two such ligands are bound such that the 'spare' pyrazine nitrogen atoms are positioned approximately orthogonally to one another and also to the imide oxygen atoms. In MeCN the [M(II/III)(pypzca)(2)](0/+) complexes, where M = Ni, Co or Fe, exhibit one reversible metal based M(II/III) process and two distinct, quasi-reversible ligand based reduction processes, the latter also observed for M(II) = Zn. [Mn(II)(pypzca)Cl(2)]HNEt(3) displays a quasi-reversible oxidation process in MeCN, along with several irreversible processes. Both copper(II) complexes show only irreversible processes. Variable temperature magnetic measurements show that [Fe(III)(pypzca)(2)]ClO(4) undergoes a gradual spin crossover from partially high spin at 298 K (3.00 BM) to fully low spin at 2 K (1.96 BM), and that [Co(II)(pypzca)(2)] remains high spin from 298 to 4 K. All of the complexes are weakly coloured, other than [Fe(II)(pypzca)(2)] which is dark purple and absorbs strongly in the visible region.     

Tripodal imidazole frameworks: Reversible vapour sorption both with and without significant structural changes

A series of tripodal imidazole frameworks (TIFs) are reported based on a tripodal, cavity-containing tris(imidazole) derivative. In the case of [Co(3)Cl(6)(1)(2)]·n(solvent) (TIF-1) which possesses a doubly interpenetrated framework structure, the material exhibits rigid, permanent porosity and selectively absorbs CO(2). The non-interpenetrated [Co(1)(2)(H(2)O)(2)]Cl(2)·4H(2)O (TIF-2) also absorbs gases and vapours fully reversibly exhibiting a reversible phase change in the process and considerable conditioning and hysteresis. The very highly hydrated [Co(1)(2)]Cl(2)·22H(2)O (TIF-3) irreversibly dehydrates to the layered structure [Co(1)(2)]Cl(2)·H(2)O (TIF-4). A nickel analogue [Ni(1)(2)]Cl(2)·22H(2)O (TIF-5) closely related to TIF-3 is also reported along with two isostructural, non-porous materials [MCl(2)(1)] (M = Mn, TIF-6; M = Cd, TIF-7) based on d(5) and d(10) Mn(II) and Cd(II). Some of the materials may be prepared by mechanochemical as well as solution based methods. We liken TIF-1 to a gas cylinder, TIF-2 to a sponge and TIF-3 to a fragile soda can that is crushed on emptying to give TIF-4.     

New molecular complexes of fullerenes C60 and C70 with tetraphenylporphyrins [M(tpp)], in which M=H2, Mn, Co, Cu, Zn, and FeCl

New molecular complexes of fullerenes C60 and C70 with tetraphenylporphyrins [M(tpp)] in which M-H2, MnII, CoII, CuII, ZnII and Fe(III)Cl, have been synthesised. Crystal structures of two C60 complexes with H2TPP, which differ only in the number of benzene solvated molecules, and C60 and C70 complexes with [Cu(tpp)] have been studied. The fullerene molecules form a honeycomb motif in H2TPP.2C60. 3C6H6, puckered graphite-like layers in H2TPP.2C60.4C6H6, zigzag chains in [Cu(tpp)].C70.1.5C7H8.0.5C2HCl3 and columns in [Cu(tpp)]2.C60. H2TPP has van der Waals contacts with C60 through nitrogen atoms and phenyl groups. Copper atoms of the [Cu(tpp)] molecules are weakly coordinated with C70, but form no shortened contacts with C60. The formation of molecular complexes with fullerenes affects the ESR spectra of [M(tpp)] (M = Mn, Co and Cu). [Mn(tpp)] in the complex with C70 lowers its spin state from S = 5/2 to S = 1/2, whereas [Co(tpp)] and [Cu(tpp)] change the constants of hyperfine interaction. ESR, IR, UV-visible and X-ray photoelectron spectroscopic data show no noticeable charge transfer from the porphyrinate to the fullerene molecules.