手性配合物[M(bipy)_3]~(2+)(M=Fe,Ru,Os)圆二色谱的理论解析

应用密度泛函理论,在DFT/B3LYP/LanL2DZ水平上优化了铁族配合物[M(bipy)3]2+(M=Fe,Ru,Os;bipy=2,2′-联吡啶)在溶液中的基态几何结构,并用TDDFT/B3LYP方法和相同的基组计算了该类配合物的激发能、旋转强度和振子强度,绘制了相应的圆二色谱.计算的谱带位置虽有一定的红移或蓝移,但各谱带的带形和符号均与实验谱吻合.对跃迁性质的分析表明,三个配合物在长波区,除[Fe(bipy)3]2+的第一个谱带是以d-d跃迁为主外,其他谱带均是荷移跃迁为主.短波区的两个强带则是以π-π*跃迁为主的激子耦合带:对于铁配合物,TDDFT可以正确预言其正负带的强度比,但对钌和锇配合物而言,由于对激子跃迁中荷移成份的贡献估计不足,计算的比值偏小.这一结论为进一步改进有关的计算模型指明了方向.     

4,7-二苯基-1,10-二氮杂菲与d10组态金属离子Zn2+、Cd2+、Hg2+配位过程的研究

用NMR与光度分析联用的方法对4,7-二苯基-1,10-二氮杂菲与d¹⁰组态金属Zn²⁺、Cd²⁺、Hg²⁺的配位机理进行了探讨,确定了配合物组成并对配合物结构及其中弯曲配键进行了推断,提出了一种从实验直接研究无d-d跃迁的以d¹⁰离子为中心的配合物配位过程以及难分离配合物配位构型测定的方法。     

固体CD光谱研究及其应用于手性席夫碱M(II)配合物

结合课题组近期的相关研究, 对固体CD光谱在手性配合物研究中的应用, 特别是手性样品固体CD光谱的测试方法进行了概述, 通过对四对手性席夫碱M(II) (M = Ni、Cu)配合物的固体和溶液CD光谱进行比较研究, 发现配合物的手性构型在固液相中保持一致, 但其固液CD光谱之间存在不同程度的差异, 可能是由于相应配合物在固体和溶液相中的四面体扭曲或构象的微妙不同所致.     

固体CD光谱研究及其应用于手性席夫碱M(II)配合物

结合课题组近期的相关研究,对固体CD光谱在手性配合物研究中的应用,特别是手性样品固体CD光谱的测试方法进行了概述,通过对四对手性席夫碱M(II)(M=Ni、Cu)配合物的固体和溶液CD光谱进行比较研究,发现配合物的手性构型在固液相中保持一致,但其固液CD光谱之间存在不同程度的差异,可能是由于相应配合物在固体和溶液相中的四面体扭曲或构象的微妙不同所致.     

三价镧系元素离子Nd~(3 )、Gd~(3 )和Tm~(3 )与肾上腺素的配合物研究

本文采pH电位滴定法和电子光谱法进行了肾上腺素与f区元素[Nd~(3 )、Gd~(3 )和Tm~(3 )]溶液的反应机理、配合物组成、配位原子位置、配位键性质和配合物稳定性等方面的研究。肾上腺素对Nd~(3 )和Tm~(3 )的f-f电子跃迁产生了微扰作用,致使其配合物的吸收谱线红移。在350～650nm区间内,三种f区离子形成的配合物的吸收光谱随pH值的提高而发生紫移现象。     

络合物光谱中d-d跃迁的机理

络合物的紫外可见光谱乃络合物中过渡金属离子的 d 电子产生 d-d 跃迁的结果,这是人们所熟知的事实。然而,d-d 跃迁却属于不符合选择定则的所谓禁阻跃迁。那么,为何禁阻跃迁能产生光谱?难道,在络合物光谱中允许跃迁和禁阻跃迁没有区别?亦或络合物中 d-d 跃     

两种4-氨基安替比林席夫碱-Pt(Ⅱ)配合物电子光谱性质的理论研究

采用密度泛函理论(DFT),在PBE0/6-31+G(d)-LANL2DZ水平下,对两种含有不同取代基的4-氨基安替比林席夫碱-Pt(Ⅱ)配合物A和B的几何构型、前线分子轨道及其分布特征进行理论计算.在优化构型的基础上,用含时密度泛函理论(TD-DFT)在相同水平下对上述配合物进行电子吸收光谱研究.计算还考虑了二氯甲烷溶剂对电子结构和光谱性质的影响.结果表明,配合物A和B的最强吸收波长分别来自于HOMO→LUMO和HOMO-5→LUMO的跃迁,以上跃迁存在明显的分子内电荷转移的特征.此外,在4-氨基安替比林配体上引入强的给电子基团-N(CH3)2,配合物A的最大吸收波长相对于配合物B发生了红移现象.     

离子对间电荷转移配合物：阴离子…π作用及近红外吸收（英文）

合成并表征了一种离子对配合物1,[Cl2Bz-1-Apy]2[Ni（mnt）2],其中,Cl2Bz-1-Apy为（E）-1-（3,4-二氯苯亚甲基氨基）吡啶一价阳离子,mnt是马来二睛基二硫烯二价阴离子。在配合物1的晶体中,阴离子和阳离子中吡啶环之间存在阴离子…π相互作用。DFT电荷密度分布分析表明,阴离子…π相互作用主要源自离子对间的Coulomb吸引力。在固体和乙腈溶液电子吸收光谱近红外区,配合物1都有一个宽的弱吸收带,该吸收带可归属为二价阴离子[Ni（mnt）2]2-内的d-d电子跃迁和阴阳离子对间的电荷转移跃迁。     

含轴向咪唑配体的手性SalenCo(Ⅲ)配合物ECD谱的理论解析

用密度泛函理论(DFT)方法,在B3LYP和混合基组(C,H原子用6-31G*;Co,N,O用6-311+G(2d,p))水平上,对含轴向配体的三种Co(Ⅲ)席夫碱配合物[Co(MeO-salen)(Im)2]+、[Co(MeO-salen)(2-Melm)2]*和[Co(MeO-salen)(Melm)2]+(Im=咪唑,Melm=1-甲基咪唑,2-Melm=2-甲基咪唑,MeO-salenH2=salen型席夫碱,即(R,R)-N,N'-双(5-甲氧基亚水杨基)-1,2-二亚胺基环己烷)在二氯甲烷溶液中的基态结构进行了优化,并用含时密度泛函理论(TDDFT)方法,在相同泛函和基组水平上计算了其激发能、振子强度和旋转强度.这些计算中均用极化连续介质模型(PCM)考虑了溶剂效应.计算的电子圆二色(ECD)谱与实验谱吻合较好.通过对有关跃迁性质的分析,对实验电子圆二色光谱进行了解析与指认.结果表明,长波区的第一个圆二色(CD)吸收带主要是由π→d荷移跃迁(LMCT)引起的,而不是通常认为的d→d跃迁.轴向配体的加入对配合物前两个CD吸收带的符号没有影响,但会影响带形和强度.手性salen配合物的绝对构型为λ(RR)时,第一个CD吸收带为正,第二个为负.这些结论对于深入理解该类配合物的电子结构和手征光学性质具有重要的科学意义.     

镍催化体系合成顺式聚丁二烯的研究——Ⅶ.紫外可见光谱法探讨镍系各组分间的相互作用

环烷酸镍的汽油或甲苯溶液呈亮绿色,根据自旋允许d-d跃迁,在光谱的红和兰区有三个吸收带,其峰值分别是403、680和1170nm,络合物具有八面体构型。在Ni-Al体系中,当Al/Ni摩尔比<0.53,只发生配位体的交换反应,Al/Ni≥0.53,体系中发生还原反应,Ni(II)→Ni(I)→Ni(O)。在Ni-B体系中,只发生配位体交换反应,生成的氟-硼-镍络合物具有和环烷酸镍相类似的d-d吸收带,络合物也具有八面体构型。以上结论与磁化率法的结果一致。     

Novel oxygen chirality induced by asymmetric coordination of an ether oxygen atom to a metal center in a series of sugar-pendant dipicolylamine copperII complexes

Six sugar-pendant 2,2'-dipicolylamine (DPA) ligands (L1-3 and L'1-3) have been prepared. OH-protected and unprotected D-glucose, D-mannose, and D-xylose were attached to a DPA moiety via an O-glycoside linkage. X-ray crystallography of the copper(II) complexes (1-5) with these ligands revealed that the anomeric oxygen atom is coordinated to the metal center in the solid state, generating a chiral center at the oxygen atom. The CD spectra of these copper complexes in methanol or aqueous solution exhibit Cotton effects in the d-d transition region, which indicates that the ether oxygen atoms remain coordinated to the metal center and the oxygen-atom chirality is preserved even in solution. For complexes 1 and 2, the inverted oxygen-atom chirality and chelate-ring conformation in the solid state are well correlated with the mirror-image CD spectra in methanol solution. The concomitant inversion of the asymmetric configuration around the copper center was also observed in a methanol solution of complex 3 and a pyridine solution of complex 2. The square-pyramidal/octahedral copper(II) centers also exhibited characteristic absorption and CD spectra.     

The electronic structure and spectra of spin-triplet ground state bis(biuretato)cobalt(III) coordination compounds

The planar coordination compounds of cobalt(III) with bis(biuretato) ligands are highly unusual due to their intermediate spin triplet ground state. Density functional theory (DFT) and time-dependent DFT have been applied in a study of the structure and electronic spectroscopy of this type of coordination compounds. The investigations included prediction and spectroscopic measurements of the absorption and circular dichroism (CD), as well as an experimental study of the magnetic CD. The results obtained by TD-DFT were in excellent agreement with the observed spectral features, both regarding the d-d and the charge transfer regions. There was noted a systematic blue-shift of the TD-DFT results compared to experiment, corresponding to an offset of ca. 0.5 microm(-1) and a scaling factor of 1.25 for the transition energies. The DFT results are rationalized in terms of a qualitative MO analysis.     

Asymmetric sulfur atom coordination in a copper(II) dipicolylamine (DPA) complex with a thioglycoside ligand

The 2,2'-dipicolylamine (DPA)-tethered thioglycoside ligand, N,N-bis(2-pyridylmethyl)-2-aminoethyl 1-deoxy-1-thio-2,3,4,6-tetra-O-acetyl-beta-d-glucopyranoside (sL1), has been prepared and its copper(II) complex synthesized. Using copper(II) chloride, the copper complex was isolated as a chloride-bound species formulated as [Cu(sL1)Cl(ClO(4))](1). The corresponding O-glycoside complex ([Cu(L1)Cl](ClO(4)), 2) was also prepared using L1 (N,N-bis(2-pyridylmethyl)-2-aminoethyl 2,3,4,6-tetra-O-acetyl-beta-d-glucopyranoside), and both complexes were characterized and compared by means of X-ray crystallography, cyclic voltammetry, electronic absorption and circular dichroism (CD) spectra. Although both complexes exhibited similar copper coordination geometries, the absolute configuration of the O/S chiral center generated by the copper coordination was inverted. The electronic and CD spectra of acetonitrile solutions of 1 and 2 were different likely due to the presence of a copper-sulfur charge-transfer band for 1. Complex also exhibits a large Cotton effect around 700 nm. The corresponding d-d transition of the copper(II) center reveals that the asymmetric copper-sulfur (oxygen) coordination remains even in solution.     

Electronic spectra of Cu(II) crystal complexes with S-methylthiosemicarbazones

Electronic spectra for a series of coordination compounds of copper(II) with tridentant ligands of salicyl aldehyde S-methylthiosemicarbazone and 8-quinoline aldehyde S-methylthiosemicarbazone were investigated. Coordinations of central ions were determined on the basis of X-ray data and IR spectra. Electronic transitions were detected by processing the diffusion-reflection spectra according to theKubelka-Munk theory. Identifications proved the presence of bands corresponding to intraligand transition, charge transfer spectra and the transition of d-d type which are the result of the elimination of d-orbital degeneration for Cu(II) ions in the crystal field. The effect of the symmetry of coordination polyhedrons is discussed.

---

Elektronenspektren von Cu(II) Kristall-Komplexen mit S-Methylthiosemicarbazonen

Zusammenfassung Es wurden Elektronenspektren einer Serie von Koordinationsverbindungen des Kupfer(II) mit tridentaten Liganden (Salizylaldehyd-S-methylthiosemicarbazon und 8-Chinolinylaldehyd-S-methylthiosemicarbazon) untersucht. Die Zentralionkoordination wurde durch Röntgenstrahlenuntersuchungen und auf Grund der IR-Spektren festgestellt. Die Elektronenübergänge wurden nach derKubelka-Munk-Theorie aus den diffusen Reflexionsspektren ermittelt. Die Banden wurden den Intraligandübergängen, dem charge-transfer-Spektrum und den d-d-Typ-Übergängen, die als Resultat der Entartungsbeseitigung der Cu(II)-d-Orbitale im Kristallfeld verschiedener Symmetrie entstehen, zugeschrieben.

     

Coordination of thrombolytic Pro-Ala-Lys peptides with Cu (II): leading to nanoscale self-assembly, increase of thrombolytic activity and additional vasodilation

Vasodilation is one of the biologically important properties for thrombolytic agents because of it may help thrombolysis via dilating blood vessels. Aimed at discovering agents with the dual-action of vasodilative and thrombolytic activities, H-Pro-Ala-Lys (PAK, 3a) and five novel analogs H-Pro-Ala-AA ( 2b-f, AA = Val, Phe, Ser, Glu, and His) were coordinated with Cu(II) to form Cu(II)-Pro-Ala-AA [( 3a-f) -Cu(II)]. The coordination chemistry was confirmed by the d-d transition occurred in their UV and circular dichroism (CD) spectra and the molecular ion in their electrospray ionization mass spectrometry (ESI-MS) spectra. The particle size tests of their solution and powders revealed that the coordination generally resulted in nanoscale self-assembly. Zeta potential and half-peak width tests indicated that the formed nanoparticles were sufficiently stable during the monitored 8 days. The bioassays implied that comparing to the PAK peptides themselves and CuCl 2 the coordination led to a 3000-fold increase of the in vitro thrombolytic activity, a 10-fold increase of the in vivo thrombolytic activity, and especially an additional vasodilation. Thus Cu(II)-peptide coordination indeed is a way for thrombolytic peptide design.     

Investigation of aromatic hydroxyoxime-transition metal complexes by infrared spectroscopy

The preparation and infrared spectroscopic studies of coordination compounds of salicylaldoxime, 2-hydroxy-acetophenone oxime, 2-hydroxy-benzophenone oxime and 2-hydroxy-4-methoxy-benzophenone oxime with copper (II), nickel (II), cobalt (II) and iron (II) are described. The frequency of the C=N stretching vibration is usually higher in the complex than that in the ligand. The higher this frequency is, the larger the stability constant of the complex will be, but there is no quantitative relationship. In the case of complexes of salicylaldoxime with Cu (II), Ni (II), Co (II) and Fe (II), v_O=N values are correlated linearly with the ionization potentials of the central metal ions. The frequency of the OH stretching vibration is closely related to the geometric configuration of the complex. Thus aromatic hydroxyoximes form coordination compounds with Co (II) and Fe (II) with cis configuration possessing six-membered hydrogen-bonded ring. This is indicated in the infrared spectra by the complete absence of the OH stretching band, or by the appearance of an extremely broad and flat band of very low intensity. However, Cu (II) or Ni (II) complex possesses trans configuration with five-membered hydrogen-bonded bridge showing characteristic OH absorption band in the infrared region. The v_oh's of complexes investigated are closely related to the polar nature of substituents on the benzene ring. By examining the spectra of ⁶³Cu and ⁶⁵Cu complexes with 2-hydroxy-4(5)-substituted benzophenone oximes in the far infrared region, the characteristic frequency of M-O and M-N were assigned for a series of aromatic hydroxyoxime-transition metal complexes.     

Stereocontrol by a pair of epimeric sugar-derived ligands of the coordination sphere of copper(II) complexes

A pair of novel C3-epimeric sugar-derived ligands (glycoligands) with a neutral N4O donor set was synthesized. Copper(II) complexes of both ligands were obtained and characterized by X-ray crystallography. Cyclic voltammetry, electron paramagnetic resonance, and UV-vis spectroscopies showed similar electronic properties. Mirror-image CD spectra were obtained for the Cu(II) d-d band, indicating an enantiomeric character of the coordination sphere, which has been rationalized structurally. This example shows the possible predetermination of stereochemistry for complexes by ligands based on a glycoscaffold.     

Vibrational circular dichroism spectroscopy of a spin-triplet bis-(biuretato) cobaltate(III) coordination compound with low-lying electronic transitions

Vibrational absorption (VA) and vibrational circular dichroism (VCD) spectroscopy was applied in the analysis of vibrational and low lying electronic transitions of a triplet ground state cobalt(III) coordination compound. The spectroscopic measurements were performed on the tetrabutylammonium salt of (6S,7S)-1,3,5,8,10,12-hexaaza-2,4,9,11-tetraoxo-6,7-diphenyl-dodecanato(4-)cobaltate(III) in DMSO solution and in potassium bromide pellets. The chiral anion exhibits an unusual geometry for cobalt(III), being four-coordinate, planar, and paramagnetic with an intermediate spin state. The spectroscopic results were compared to measurements performed on the free ligand and to theoretical calculations using density functional theory (B3LYP/TZVP). The results of the VCD analysis of the coordination compound identified an electronic, dipole-forbidden, magnetic dipole-allowed low-lying d-d transition located in the mid infrared, as well as several amide stretch transitions located in the fingerprint region (1800-1100 cm(-1)), in both the liquid and solid phase. VCD signals were found to be 5-10 times higher than expected, indicating enhancement of the vibrational CD signals, caused by coupling of the vibrational transitions with the close-lying electronic transition.     

某些芳香族羟肟一过渡金属配合物的红外光谱

The preparation and infrared spectroscopic studies of coordination compounds of salicylaldoxime, 2-hydroxy-acetophenone oxime, 2-hydroxy-benzophenone oxime and 2-hydroxy-4-methoxy-benzophenone oxime with copper (II), nickel (II), cobalt (II) and iron (II) have been described. The frquency of the C=N stretching vibration is usually higher in the complex than that in the ligand. The higher the frequency of the C=N vibration is, the larger the stability constant of the complex will be, but there is no quantitative relationship. In the case of complexes of salicylaldoxime with Cu, Ni, Co and Fe, &CC=N values are correlated linearly with the ionization potentials of the central metal ions. The frequency of the OH stretching vibration is closely related to the geometric configuration of the complex. Thus aromatic hydroxyoximes form coordination compound with Co (II) and Fe (II) with cis configuration possessing six membered stronger hydrogen bonding ring. This is indicated in the infrared spectra by the complete absence of the absorption band due to the OH stretching vibration, or by the appearance of an extremely broad and flat band of very low intensity. However, Cu (II) or Ni (II) complex possesses trans configuration with five membered hydrogen-bonding bridge showing characteristic OH absorption band in the infrared region. The &COH of complex investigated is closely related to the polar nature of the substituents on the benzene ring. By examining the spectra of Cu-63 and Cu-65 complexes with 2-hydroxy-4(5)-substituted benzophenone oximes, the characteristic frequencies of M -- O and M -- N in the far infrared region were assigned for a series of aromatic hydroxyoxime-transition metal complexes.