Synthesis and Characterization of [Cu(N-MeIm)4(BF4)2] in Ionic Liquid

A new transition metal complex, [Cu(N-MeIm)₄(BF₄)₂](N-MeIm=N-methylated imidazoles, BF₄= tetrafluoroborate), was synthesized via the solvothermal method in ionic liquid. The ionic liquid acts as thermal decomposition reaction medium, soft temple agent and ligand compound. The central Cu(II) ion is coordinated by four N atoms from four N-methylated imidazole ligands, and the four N-methylated imidazole rings are perpendicular to each other. The crystal structure of [Cu(N-MeIm)₄(BF₄)₂] was determined by single crystal X-ray diffraction. The results of thermogravimetry(TG) and Fourier transform infrared spectrometry(FTIR) analyses were in accordance with that of crystal structure. The complex showed strong ligand-based absorbance with maximum wavelength at 208 and 231 nm, which are attributed to π-π^* transition of the N-methylated imidazole ligands.     

Racemic atropisomeric N,N-chelate ligands for recognizing chiral carboxylates via Zn(II) coordination: structure, fluorescence, and circular dichroism

Two racemic atropisomeric N,N'-chelate ligands, bis{3,3'-[N-Ph-2-(2'-py)indolyl]} (1) and bis{3,3'-N-4-[N-2-(2'-py)indolyl]phenyl-2-(2'-py)indolyl} (2), have been found to be able to distinguish the enantiomers of Zn((R)-BrMeBu)2 and Zn((S)-BrMeBu)2 where BrMeBu = O2CCH(Br)CHMe2, with a distinct and intense CD spectral response at approximately the 10 microM concentration range. Computational studies established that the (R)-1-Zn((R)-BrMeBu)2 or (S)-1-Zn((S)-BrMeBu)2 diastereomer is more stable than (R)-1-Zn((S)-BrMeBu)2 or (S)-1-Zn((R)-BrMeBu)2. In addition, computational studies showed that the CD spectra of (S)-1-Zn((S)-BrMeBu)2 and (S)-1-Zn((R)-BrMeBu)2 are similar. (1)H NMR spectra confirmed that these two diastereomers exist in solution in about a 2:1 ratio for both complexes of 1 and 2. The distinct CD response of the racemic ligands 1 and 2 toward the chiral zinc(II) carboxylate is therefore attributed to the preferential formation of one diastereomer. The binding modes of the zinc(II) salt with ligands 1 and 2 were established by the crystal structures of the model compounds 1-Zn(tfa)2 and 2-Zn(tfa)2 (tfa = CF3CO2(-)), where the Zn(II) ion is chelated by the two central pyridyl groups in the ligand. Fluorescent titration experiments with various zinc(II) salts showed that the fluorescent spectrum of the atropisomeric ligand displays an anion-dependent change. The zinc(II) binding strength to the N,N'-chelate site of the atropisomeric ligand has been found to play a key role in the selective recognition of different chiral zinc(II) carboxylate derivatives by the racemic atropisomeric ligands.     

新型手性酪氨酸卟啉锌对咪唑类客体的分子识别研究

合成了两种新型手性锌卟啉Zn(o-BocTyr)TAPP和Zn(p-BocTyr)TAPP.通过元素分析、紫外可见光谱及核磁共振谱对其性质进行了表征.研究了这两种锌卟啉对咪唑类的分子识别行为,识别的缔合常数顺序均为K(2-MeIm)>K(Im)>K(N-MeIm)>K(2-Et-4-MeIm).同时,采用理论计算和圆二色谱研究了咪唑类小分子在与锌卟啉分子识别时进攻主体位置的变化,这对于研究卟啉分子识别起到一定的作用.     

新型1,1′-双(4,5-二烷基)咪唑二茂铁的合成及其晶体结构

1,1′-二茂铁二甲醛与烷基二酮反应合成了3种新型的1,1′-双(4,5-二烷基咪唑)二茂铁,其结构经1HNMR,13C NMR,IR,ESI-MS及元素分析表征。1,1′-双(4,5-二苯基咪唑)二茂铁醋酸盐(1a′)的晶体结构经X-射线单晶衍射表征。1a′的晶体结构显示二茂铁的两个取代咪唑通过与醋酸的氢键作用形成顺式构型,探讨了顺式构型与反式构型的转化条件。1a′属单钭晶系,C2/c空间群,晶胞参数:a=15.832(4),b=19.255(4),c=14.781(4),β=121.837(3)°,V=3828.0(15)3,Z=4,F(000)=1 687,Dc=1.395 g.cm-3,Mr=804.07。     

Synthesis and photochromism of dimers of 4,5- diaryl-2-(2,5-dimethylthiophen-3-yl)imidazolyl

4,5-Diphenyl, 4,5-di(4-methylphenyl), 4,5-di(4-methoxyphenyl)-2-(2,5-dimethylthioph-en-3-yl)imidazoles were synthesized. Oxidation of the obtained imidazoles with potassium ferricyanide in water-alcohol solution of alkali gave the corresponding dimers. The structures were characterized by IR, 1H NMR, mass spectroscopy and elemental analysis. The dimers showed photochromism in solution on irradiation.     

Photosensitized oxidation of 13C,15N-labeled imidazole derivatives

An efficient synthesis of imidazoles with isotope labeling at different positions of the five-membered ring was developed. We carried out a detailed mechanistic study of the photosensitized oxidation of isotope-labeled imidazole derivatives. A new product, CO(2), was observed in the photooxidation of 2-H,N1-H imidazoles, but not in 2-substitituted imidazoles. The carbon of CO(2) derives from the 2C of imidazole. As shown by 18O experiments, both oxygen atoms of CO(2) originate mainly from one molecule of oxygen. Transient intermediates were detected by low-temperature NMR in the photosensitized oxidation of the isotope-labeled imidazoles. Quantitative analysis of the 13C NMR at different temperatures and times correlates the formation of one intermediate with the loss of another, thus allowing the complete decomposition pathway of the transient intermediates to be established. Singlet oxygen reacts with 4,5-diphenylimidazole via a [4 + 2] cycloaddition to form a 2,5-endoperoxide, which, upon warming, decomposes to a hydroperoxide. The hydroperoxide in one pathway loses water to form an imidazolone 7, which is hydrolyzed to a hydroxyimidazol-2-one 11. In another pathway, the hydroperoxide rearranges to diol 8. The diol rearranges to a carbamate 9 by opening and reclosing the five-membered ring. 9 decomposes to CO(2) and benzil diimine. A labile NH in the imidazole is crucial for the decomposition of the initially formed endoperoxide, otherwise the endoperoxide decomposes to regenerate starting material. Many similarities exist between the photooxidations of imidazole and guanosine in organic solvent, suggesting that the two reactions share a similar reaction mechanism with singlet oxygen.     

Design and synthesis of a self-assembled photochemical dyad based on selective imidazole recognition

The unique recognition properties of phenanthroline-strapped zinc porphyrin 1, which displays extremely high affinity for N-unsubstituted imidazoles, has been used as the driving force for the assembly of a photochemical dyad involving a zinc(II) porphyrin as energy donor and a free base porphyrin as energy acceptor. The synthesis of the imidazole-substituted porphyrin is described together with the assembly of the dyad. (1)H NMR titrations confirm the formation of a 1/1 complex between 1 and 6, as well as insertion of the imidazole of the acceptor within the phenanthroline strap of the donor. Preliminary fluorescence quenching measurements show that efficient energy transfer occurs between the self-assembled components.     

Built-in axial base binding on phenanthroline-strapped zinc(II) and iron(III) porphyrins

In addition to the need for functional models of cytochrome c oxidase, structural models are still required for a better understanding of the small reorganizations occurring during the catalytic cycle. An efficient synthetic approach has been designed to prepare several phenanthroline-strapped porphyrins, two of them bearing two pendant imidazoles. These built-in bases are both potentially able to act as axial bases for the metalloporphyrin and as complementary ligands for copper if necessary. Diamagnetic zinc(II) was used to demonstrate that the distal/proximal selectivity demonstrated by exogenic bases binding studies can be extended to the coordination of iron(III). Combination of EPR and paramagnetic 1H NMR shows that the imidazole binding on the zinc species can be further extended to the iron(III) species in dilute conditions.     

含甲基咪唑的抗肿瘤转移NAMI-A衍生物的水解和电化学性质

合成了trans-[Rucl4 (DMSO) (4-MeIm)][(4-MeIm)H]·HCl(4-MeIm=4-甲基咪唑)(1)和trans-[Rucl4 (DMSO)(N-MeIm)][(N-MeIm)H](N-MeIm=N-甲基咪唑)(2).通过紫外-可见光谱、核磁共振谱和循环伏安法研究了配体结构(4-甲基咪唑,...     

二(2-氨乙基)-1，3-丙二胺与镍(Ⅱ)的配合物的合成和晶体结构

本文报道了二(2-氨乙基)-1,3-丙二胺［缩写为(2,3,2)］与镍的两个新配合物：［(2,3,2)Ni(ImH)₂］(ClO₄)₂和［(2,3,2)₂Ni₂(Im)］(ClO₄)₃的合成和晶体结构(其中ImH是咪唑)。配合物［(2,3,2)Ni(ImH₂)］(ClO₄)₂属于正交晶系,空间群Pna2₁, 晶胞参数为：a=16.798(3), b=15.724(3), c=8.891(2)?,Z=2。R₁=0.0566, wR₂=0.0659。在配合物正离子中,Ni与(2,3,2)的四个配位N原子和两个咪唑的两个配位N原子构成NiN_{6的八面体配位构型,(2,3,2)采取顺式构象。配合物［(2,3,2)2Ni2(Im)］(ClO4)3属于单斜晶系,空间群C2,晶胞参数为：a=12.044(1), b=12.224(2), c=11.868(1)?;β=108.04°;Z=2, R1=0.0384, wR2=0.0516。在配合物正离子中,咪唑桥联两个等价的(2,3,2)Ni,每个镍原子都有四方锥的配位环境,(2,3,2)的四个配位N原子构成赤道平面,咪唑N原子占据轴向位置,分子内两个金属间的距离为6.190(3)?。}     

Synthesis of some novel tetracyclic imidazole derivatives

Representatives have been made of three new heterocyclic systems (IIH) containing an imidazole ring. Synthetic routes are described for compounds of type II where X = CH₂ (8H-dibenzo[3,4: 6,7]cyclohept[1,2-d] imidazoles), and X = CH₂CH₂ (8,9-dihydrodibenzo[3,4:7,8]cyclooct[1,2-d] imidazoles) and X = S (dibenzo[2,3:6,7] thiepin] 4,5-d] imidazoles). In addition, improved syntheses are presented for some previously known compounds employed as intermediates in this work.     

STRUCTURES AND PROPERTIES OF COPPER(II) COMPLEXES WITH IMINODIACETATO AND IMIDAZOLE OR RELATED LIGANDS. I. CRYSTAL STRUCTURE OF AQUA(IMIDAZOLE) (IMINODIACETATO)COPPER(II) MONOHYDRATE AND (IMIDAZOLE)(N-CARBOXYMETHYL-D,L-THREONINATO)COPPER(II)

Abstract

The crystal structures of two mixed-ligand copper(II) complexes having iminodiacetate(2-) (IDA) or N-carboxymethyl-D,L-threoninato(2-) ion (CMT) as terdentate ligands and imidazole (ImH) as an N-heterocyclic ligand are reported. Both compounds crystallize in the orthorhombic system, space group Pbca with Z = 8. Aqua(imidazole)(iminodiacetato)copper(II) monohydrate (I,R = 0.065, R _w = 0.075) consists of H₂O molecules and [Cu(IDA)(ImH)(H₂O)] complex units in a hydrogen bonding network. The structure of imidazole(N-carboxymethyl)-D,L-threoninatocopper(II) (IV, R = 0.066, Rω 0.078) is built up of hydrogen bonded polynuclear chains. In both compounds the Cu(II) ion exhibits a flattened and distorted square-based pyramidal coordination, with a terdentate aminoacidate ion, IDA or CMT, and one ImH ligand at the base and H₂O (in I) or the oxygen atom of the OH side chain from one adjacent CMT ion (in IV) as the fifth apical ligand. The nearly coplanar conformation of the two five-membered chelate rings in I and IV is discussed in connection with the known structure of corresponding aquacomplexes (with H₂O instead of ImH) and the ability of terdentate aminoacids to give ternary Cu(II) complexes having two N-heterocyclic donors (2 ImH or one 2,2′-bipy) per Cu(II) atom.     

Synthesis, Characterization, and Crystal Structure of a Novel Copper(II) Complex with an Asymmetric Coordinated 2,2'-Bipyridine Derivative: A Model for the Associative Complex in the Ligand-Substitution Reactions of [Cu(tren)L](2+)?

The titled compound, (tris(2-aminoethyl)amine)(4,5-diazafluoren-9-one) copper(II) perchlorate, [Cu(C(6)H(18)N(4))(C(11)H(6)N(2)O)(ClO(4))(2)], 1, has been designed, synthesized, and characterized. The electronic and ESR spectra are very different from those of [Cu(tren)L](2+) complexes where L is monodentate ligand. The X-ray analysis revealed that the complex crystallizes in the monoclinic space group P2(1)/c, with a = 10.726(6) ?, b = 14.921(7) ?, c = 14.649(4) ?, beta = 95.13(3) degrees, and Z = 4. The copper(II) ion is coordinated by four nitrogen atoms from tris(2-aminoethyl)amine (tren) and two nitrogen atoms from 4,5-diazafluoren-9-one (dzf) to form an unusual six-coordinate (4 + 1 + 1') geometry. The structure is very rare, and to our knowledge, it is the first example of an asymmetric bidentate phenanthroline derivative metal complex. The structure could be used as a model of the associative complex in the ligand-exchange and ligand-substitution reactions of [Cu(tren)L](2+) and the catalytic mechanisms of enzymes involving copper sites. From the electronic and variable-temperature ESR spectra in solution, the possible mechanism of these reactions has also been proposed. As a comparison, the complex [Cu(tren)(ImH)(ClO(4))(2)], 2, was also synthesized and characterized, where ImH is imidazole.     

Imidazole derivatives as the organic precursor of ZnO nano particle

N₁-Hydroxy-2,4,5-trisubstituted imidazoles were synthesized starting from 1,2-diketones. The crystal structure of 4,5-dimethyl-2-(3-nitrophenyl)-1H-imidazol-1-ol has been determined. An unusual intermolecular hydrogen bonding through the association of water molecule has been reported. These imidazole derivatives can be thought of as the organic precursor for the synthesis of zinc oxide nano particles.     

2,6-di(pyrimidin-4-yl)pyridine ligands with nitrogen-containing auxiliaries: the formation of functionalized molecular clefts upon metal coordination

A series of ligands (1-4) based on a 2,6-di(pyrimidin-4-yl)pyridine scaffold have been synthesized, and their abilities to form complexes with Zn(II) and Cu(II) have been determined using UV/vis spectroscopy in buffered aqueous solution (0.01 M N-[2-hydroxyethyl]piperazine-N'-[3-ethanesulfonic acid] (HEPES) at pH = 6.8). The Zn(II) complex of 1 was determined to have a formation constant of 8.4 x 10(3) M(-)(1) while the formation constant of the Cu(II) complex was found to be 1 x 10(6) M(-)(1). The presence of auxiliary amines in 2 increased the stability of the Zn(II) complex relative to that of 1 by a factor of over 40, suggesting possible coordination of the auxiliaries to the Zn(II) center. The guanidinium and 2-amino-4,5-dihydro-imidazolinium groups of 3 and 4 considerably diminished the stability of the Zn(II) and Cu(II) complexes relative to those of 1. X-ray crystal structures of 1-Zn, 3-Zn, 4, and 4-Zn were obtained and are discussed. A significant increase in the stability of 3-Zn, but not in the stability 1-Zn, was observed upon the addition of 1 equiv of sodium phosphate, implicating a stabilizing interaction of the guanidinium groups of 3-Zn and the phosphate anion.     

手性锌卟啉的热力学性质及其理论计算研究

通过紫外-可见光谱滴定法和圆二色光谱法，对手性锌卟啉化合物(ZnP)与4种咪唑类小分子的轴向配位反应的热力学性质进行了研究。测定的热力学数据和圆二色光谱的实验结果显示，配位常数按K(2-MeIm)>K(Im)>K(N-MeIm)>K(2-Et-4-MeIm)的顺序依次减弱，咪唑类配体的轴向配位能力按2-Et-4-MeIm<N-MeIm相似文献   

Synthesis of Bi- and tridentate imidazole ligands

A number of imidazole derivatives were prepared in the course of studying the limits of carbon-metal bond formation in complexes of imidazole with first-row transition metals. Seven of the compounds were new. The 4- and 5-methyl and 4,5-dimethyl derivatives of l-(2-pyridyl)-imidazole were prepared by reaction of the appropriate imidazole with 2-bromopyridine. Alkylation of imidazole, 4,5-dimethylimidazole, and benzimidazole with 2-chloromethylpyridine gave a series of 1-(2-pyridylmethyl)imidazoles. 1-(2,3-Diaminopropyl)imidazole was prepared in six steps via a Gabriel sequence.     

Two different hydrogen bond donor ligands together: a selectivity improvement in organometallic {Re(CO)3} anion hosts

Rhenium(I) compounds [Re(CO)(3)(Hdmpz)(2)(ampy)]BAr'(4) and [Re(CO)(3)(N-MeIm)(2)(ampy)]BAr'(4) (Hdmpz = 3,5-dimethylpyrazole, N-MeIm = N-methylimidazole, ampy = 2-aminopyridine or 3-aminopyridine) have been prepared stepwise as the sole reaction products in good yields. The cationic complexes feature two different types of hydrogen bond donor ligands, and their anion binding behavior has been studied both in solution and in the solid state. Compounds with 2-ampy ligands are labile in the presence of nearly all of the anions tested. The X-ray structure of the complex [Re(CO)(3)(Hdmpz)(2)(ampy)](+) (2) shows that the 2-ampy ligand is metal-coordinated through the amino group, a fact that can be responsible for its labile character. The 3-ampy derivatives (coordinated through the pyridinic nitrogen atom) are stable toward the addition of several anions and are more selective anion hosts than their tris(pyrazole) or tris(imidazole) counterparts. This selectivity is higher for compound [Re(CO)(3)(N-MeIm)(2)(MeNA)]BAr'(4) (5·BAr'(4), MeNA = N-methylnicotinamide) that features an amido moiety, which is a better hydrogen bond donor than the amino group. Some of the receptor-anion adducts have been characterized in the solid state by X-ray diffraction, showing that both types of hydrogen bond donor ligands of the cationic receptor participate in the interaction with the anion hosts. DFT calculations suggest that coordination of the ampy ligands is more favorable through the amino group only for the cationic complex 2, as a consequence of the existence of a strong intramolecular hydrogen bond. In all other cases, the pyridinic coordination is clearly favored.     

Autocatalytic demetalation of a Zn(salphen) complex provoked by unprotected N-heterocycles

The interaction of Zn(salphen) complex with biologically important structures such as (benz)imidazoles and purine has been studied and revealed in the case of unprotected purine and (benz)imidazole derivatives a demetalated product, whereas for structurally related 1-methyl-(benz)imidazole the formation of 1 : 1 coordination complexes was evidenced by NMR, MS and X-ray crystallography.     

Excited-state intramolecular proton transfer in 2,4,5-triarylimidazole molecules

Excited-state intramolecular proton transfer (ESIPT) in the 2,4,5-triarylimidazole molecules was studied by spectral-luminescent technique. For 4,5-diphenyl-(2-hydroxyphenyl)imidazoles, the ESIPT occurs in both liquid and glassy matrices at 77 K. For 4,5-diphenyl-(2-hydroxynaphthyl)imidazole, the ESIPT requires rotation of molecular fragments and is not observed at 77 K.