首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
A series of penta-coordinated CoII complexes of 1,4-diazacycloheptane (DACH) functionalized by additional imidazole or pyridine donor pendants, [CoL1Cl](ClO4)·H2O (1), [CoL2Cl](ClO4) (2) and [CoL3Cl](ClO4)·CH3OH (3), where L1=1,4-bis(imidazole-4-ylmethyl)-DACH, L2=1,4-bis(N-1-methylimidazol-2-ylmethyl)-DACH and L3=1,4-bis(pyridyl-2-ylmethyl)-DACH have been synthesized and characterized by elemental analyses, IR and UV–Vis spectra. In all the mononuclear complexes, each CoII center is penta-coordinated to four nitrogen donors of the ligand and one axial chloride anion. The crystal structure of complex 2 has been determined by X-ray diffraction analysis, which forms a one-dimensional linear structure through inter-molecular C–HCl and C–HO hydrogen-bonding.  相似文献   

2.
The results of experimental studies and quantum mechanical calculations of vibrational spectra and structure of hydrogen bonded complexes formed by pyrazole (P) and 3,5-dimethylpyrazole (DMP) are presented. IR spectra of pyrazoles in solutions, gas phase, and solid state have been investigated in wide range of concentrations and temperatures. It has been found that in the gas phase both P and DMP reveal the equilibrium between monomers, dimers, and trimers. In solutions the equilibrium between monomers and trimers dominates, no bands, which can be attributed to dimers were detected. DMP retains the trimer structure in solid state, while in the case of pyrazole P, formation of the crystal provides another type of association. Geometrical and spectral characteristics of dimers and trimers, obtained by ab initio calculations, are presented and compared with experimental data.

IR spectra of solutions containing P and DMP with a number of acids (acetic and trifluoroacetic acids, pentachlorophenol, HBr) have been studied in parallel with ab initio calculations. It has been found that pentachlorophenol forms with pyrazoles complexes with one strong hydrogen bond O–HN, while NH pyrazole group remains unbonded. With carboxylic acids DMP forms 1:1 cyclic complexes with two hydrogen bonds. In the case of acetic acid, the complex in CH2Cl2 solution reveals molecular structure with OHN and C=OHN bonds, in accordance with results of the calculations. For trifluoroacetic acid, the calculations predict the molecular structure to be energetically more stable in the case of the isolated binary complex (in gas phase), while the experimental spectrum of CH2Cl2 solution gives an evidence of the proton transfer with formation of the cyclic ionic pair with two NH+O bonds. The agreement with experimental results can be improved by taking into account the influence of environment in the framework of Onsager or Tomasi models. The shape of proton potential function of the complexes and medium effect on its parameters, resulted from experimental data and calculations, are discussed. It has been found that the number of potential minima and their relative depth depend strongly on the method of calculations and the basic set. Under excess of trifluoroacetic acid, the formation of 2:1 acid–DMP complex has been detected. Spectral characteristics and results of calculations point to the cyclic structure of this complex, which includes homoconjugated bis-trifluoroacetate anion and DMPH+ cation. With HBr both studied pyrazoles were found to form ionic complexes including one or two pyrazole molecules per one acid molecule and correspondingly monocation or homoconjugated cation BHB+.  相似文献   


3.
Infrared spectroscopy and matrix isolation technique have been used to study the 1 : 1 complexes formed between 2,4,5-trichlorophenol (TCP), pentachlorophenol (PCP) or 2-chloro-4,6-dinitrophenol (CNP) and trimethylamine (TMA) isolated in solid argon. The results were analyzed in relation to the type of complex formed. Depending on the proton-donor ability of the phenol three different types of hydrogen bonded complexes have been identified in argon matrices. The weakest phenol in the series, TCP (pKa = 6.72), forms a strong molecular hydrogen bonded complex with TMA as indicated by the broad ν(OHN) absorption with a maximum at 2490 cm−1 and a band at 811 cm−1 due to the νs(C3N) mode of the perturbed amine. The strongest phenol, CNP (pKa = 2.01), interacts with TMA in an argon matrix to form ionic complex with the proton transferred to the base molecule. This is evidenced by the presence of the ν(NH+---O) absorption between 3000−1800 cm−1, by the νas(C3N+) and νs(C3N+) absorptions due to the protonated amine and by numerous product bands due to the relatively strongly perturbed modes of the phenol ring. The interaction between TMA and a phenol of intermediate strength, PCP (pKa = 4.74), in solid argon probably leads to the formation of two types of hydrogen bonded complexes: an ionic complex with the proton transferred to the amine molecule and a pseudosymmetric one with the proton more or less equally shared between the phenol and amine molecules. In this case the protonic absorption consists of two broad features situated in the 3000–1600 cm−1 and 950–400 cm−1 regions due to the ν(NH+O) and ν(OHN) modes, respectively.  相似文献   

4.
Raman spectra of binary mixtures of acetonitrile (ACN) and formamide (FA) in different compositions were obtained. The appearance of a new band at 2257 cm−1, whose intensity shows large dependence on the FA concentration, is assigned to a FA–ACN adduct. This has been possible owing to the two H-bond donor sites of FA and the strong donor character of ACN, becoming the environment propitious for the donor–acceptor reaction. Quantitative measurements performed in the CN stretching region in the binary mixtures give a 1:1 stoichiometry in this adduct in the limit of infinite dilution. In the N–H stretching region of FA, the band at 3270 cm−1 is assigned to (FA–FA)n interactions, via hydrogen bonding.

The experimental evidence of the 1:1 FA–ACN adduct is presented for the first time using Raman spectroscopy. The results described here open new possibilities to study this adduct and to evaluate thermodynamics parameters of interest.  相似文献   


5.
Oxazolone forms (1:1) complexes with Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ chlorides, as well as forms (1:1) complexes with Co2+ and Cu2+ acetates. All the complexes are found to be non-electrolytes in DMF; tetrahedral, square-planar and octahedral structures are assigned to them based on electronic and magnetic data. IR studies reveal that the complexes are formed by donating the lone-pair electron from O and N atoms to the metal ion. The thermal decomposition of the [ML·mnH2O]y·H2O chelates was studied by TG–DTA techniques. The mechanism of the decomposition has been established from TG–DTA data. The kinetic parameters, activation energy (Ea) and pre-exponential factor (A), were calculated from TG curves using Coats and Redfern method. Relative thermal stabilities of the chelates have been evaluated on the basis of these parameters.  相似文献   

6.
The influence of the –NH2 group position in the pyridine ring on the proton donor ability of N–H groups in hydrogen bonding as well as on the spectral behaviour of stretching and bending vibrations of aminopyridines has been studied. The proton donor ability was shown to increase in the row: meta-, ortho-, and para-aminopyridines. It was established tha N–H bonds in ortho-aminopyridine were not equivalent, and the evaluation of their dynamic nonequivalence was made.

The influence of temperature on the spectral characteristics of the absorption bands of the stretching vibrations of amine groups in the free and hydrogen bonded molecules in CCl4 has been studied (in temperature range 290–330 K), the formation constants of the complexes have been determined, enthalpy of the 1:1 complexes formation (−ΔH1) between ortho- and meta-aminopyridines with dimethylformamide, dimethylsulphoxide and hexamethylphosphoramide has been calculated in temperature range 290–330 K. The 1:2 complexes of ortho-, meta- and para-aminopyridines with acetonitrile, tetrahydrofurane, dimethylsulphoxide, hexamethylphosphoramide were studied at the indoor temperature. Enthalpy of the 1:2 complex (−ΔH2) was estimated on the basis of ‘intensity rule’; −ΔH1B1/2 assuming that parameter does not depend on the composition of a complex.

The vibrational and electrooptical tasks were solved for the free and H-bounded molecules of aminopyridines as well as its complexes of the 1:1 and 1:2 compositions. Dynamic, electrooptical and energetic nonequivalency of NH bonds of aminogroups in aminopyridines was studied quantitatively. The independent calculations of dynamic constants proved mentioned above nonequivalency of NH bonds.

Correlations between spectral characteristics of the absorption bands, geometric, dynamic and electrooptical parameters of –NH2 group in aminopyridines in the free and hydrogen bonded molecules have been established. Those correlations allow to determine the most important molecular characteristics obtained on the basis of spectral measurements in the range of the absorption bands of the stretching vibrations of aminogroup.  相似文献   


7.
High level DFT was applied to study structure and conformational equilibrium of amino and mercaptocalix[4]arenes possessing methylene groups or sulfur atoms at their four junctions. All the calculations point to cone and 1,3-alternate as the most stable conformers for sulfur and methylene bridged compounds, respectively. The presence of four sulfur atoms in place of the methylene bridges can lead to novel features in the complexation with transition metals. The host–guest 1:1 complexes between Zn2+ and each conformer of tetraaminothiacalix[4]arene were also investigated at the same DFT level. The four nitrogens of amino groups play a dominant role in the interaction with Zn2+ via distorted tetrahedral coordination for 1,3-alternate, or distorted square planar for partial cone and 1,2-alternate. On the other hand, the 2:1 complexes with cone show that the sulfur bridges can also bind Zn2+ and contribute to form two sets of five-membered chelated rings with two N donor atoms.  相似文献   

8.
The results of X-ray diffraction and IR spectroscopic studies for 2:1 pentachlorophenol-7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene [(PCP)2·MTBD] adduct are reported. The geometry of MTBD cations reflects the equal distribution of the positive charge among three nitrogen atoms. Short asymmetric [OHO] hydrogen bonds with OO distance of 2.508(2) Å and NH+O hydrogen bonds with NO distance of 2.802(2) Å are formed showing broad IR absorption with two maxima located at 1200 and 2400 cm−1. The second maximum is interpreted as due to the 0→2 transition between split levels in an asymmetric double minimum potential. One of the oxygen atoms forms an additional OH–N+ hydrogen bonding with an MTBD cation. The situation is somewhat different in acetonitrile solution whose IR spectrum shows continuous absorption extended over whole the IR region. In acetonitrile, dissociation to free OHO and +NH ions takes place and the OHO bridges become dynamically symmetric. The broadening is interpreted in terms of a stochastic distribution of the geometry and the Zundel polarizability theory.  相似文献   

9.
Interaction of hydrated proton, H5O2+·(H2O)4, in dichloroethane solutions with diphosphine dioxides (L) having methyl (Ph4Me), ethyl (Ph4Et) and polyoxyethylene chains (Ph4PEG) linking two diphenyl phosphine oxide groups has been investigated. A bulky counter ion: chlorinated cobalt(III) bis(dicarbollide), [Co(C2B9H8Cl3)2], minimizes perturbation of the cation. At low concentrations, Ph4Et and Ph4PEG form anhydrous 1:1 complexes with (P)O–H+–O(P) fragment having very strong symmetrical H-bonds. At these conditions Ph4Me form another compound, H5O2+·L(H2O)2, due to lower PO basicity and optimal geometry of the chelate cycle. At higher concentrations, Ph4Me and Ph4Et form isostructural complexes H5O2+·L2, whereas Ph4PEG forms only a 1:1 complex with proton dihydrate, H3O+·H2O. In excess of free Ph4Me and Ph4Et a water molecule is introduced to the first coordination sphere of H5O2+ and the average molar ratio L/H5O2+ of the complexes exceeds 2. The composition of these complexes as a function of L and its concentration is discussed.  相似文献   

10.
The ability of Oligomycin A (OLA) to form complexes with monovalent cations was studied by the ESI mass spectrometry and PM5 semiempirical method. At low cone voltage values the ESI MS spectra indicate that OLA formes stable 1:1 complexes with Mg2+, Ca2+, Sr2+, Ba2+, Zn2+ divalent cations irrespective of the stoichiometry. With increasing cone voltages the formation of the [OLA + M + (ClO4 or Cl)]+ complexes was preferred. This process occurred simultaneously with the formation of fragmentary metal cation complexes with the exception of Pb2+ ions which does not form complexes with OLA molecule. PM5 semiempirical calculations allowed the visualizations of all structures of (OLA + M)2+ and [OLA + M + (ClO4or Cl)]+ complexes as well as the fragmentary cations.  相似文献   

11.
用两类结构不同的Schiff碱型、仲胺型双-(苯并-18-冠-6)在氯仿-水体系中对碱金属苦味酸盐进行萃取,测量了配合物组成比和萃取平衡常数。  相似文献   

12.
The complexes trans-[Os(CCPh)Cl(dppe)2] (1), trans-[Os(4-CCC6H4CCPh)Cl(dppe)2] (2), and 1,3,5-{trans-[OsCl(dppe)2(4-CCC6H4CC)]}3C6H3 (3) have been prepared. Cyclic voltammetric studies reveal a quasi-reversible oxidation process for each complex at 0.36–0.39 V (with respect to the ferrocene/ferrocenium couple at 0.56 V), assigned to the OsII/III couple. In situ oxidation of 1–3 using an optically transparent thin-layer electrochemical (OTTLE) cell affords the UV–Vis–NIR spectra of the corresponding cationic complexes 1+–3+; a low-energy band is observed in the near-IR region (11 000–14 000 cm−1) in each case, in contrast to the neutral complexes 1–3 which are optically transparent below 20 000 cm−1. Density functional theory calculations on the model compounds trans-[Os(CCPh)Cl(PH3)4] and trans-[Os(4-CCC6H4CCPh)Cl(PH3)4] have been used to rationalize the observed optical spectra and suggest that the low-energy bands in the spectra of the cationic complexes can be assigned to transitions involving orbitals delocalized over the metal, chloro and alkynyl ligands. These intense bands have potential utility in switching nonlinear optical response, of interest in optical technology.  相似文献   

13.
The complexation of 4-nitrocatechol in aqueous solution at pH 5 has been studied by molecular spectroscopy combined with quantum chemical calculations. In these physico-chemical conditions, the formation of the two complexes [4ncatAl(H2O)4]+ and [(4ncat)2Al(H2O)2] has been highlighted. The electronic absorption spectra of the 1:1 and 1:2 complexes of Al(III) with 4-nitrocatechol have been computed using the time-dependent density functional theory and the polarizable continuum model. It turns out that the 6-311+G(d,p) basis set provides a good agreement between experimental and theoretical absorption spectra. This good agreement has allowed the determination of the preferential conformation of the 1:2 complex in aqueous solution. A complete assignment of the UV–Vis absorption and Raman spectra of the complexes has been proposed.  相似文献   

14.
Vibrational (Raman and IR) spectra of the 1:1 complexes of dihalogermylene and dihalostannylene with 1,4-dioxane and PPh3 have been reported, the structures of the complexes Cl2Ge·C4H8O2 and Cl2Ge·PPh3 updated using high-resolution X-ray method. Quantum-chemistry calculations of the geometry and normal mode frequencies and eigenvectors were carried out for some of the complexes. The results show that in the structure of the polymeric solid complexes of X2M with 1,4-dioxane, intermolecular coordination XM plays a prominent role, whereas the corresponding complexes with PPh3 are monomeric. In the vibrational spectra of all the complexes, an inversion of symmetric and antisymmetric stretching νXM (X=Cl, Br; M=Ge, Sn) frequencies, found for ‘free’ X2MII particles, still persists, suggesting that the X2M moieties preserve their specifity as carbene analogues also in the complexes.  相似文献   

15.
Synthesis and characterization of a nitrite-bound copper(II) compound [CuL4)2(ONO)]ClO4 have been achieved (L4 = 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine]. The bidentate ligand L4 provides a pyridine and a pyrazole donor site; however, they are separated by a methylene spacer. The complex has been structurally characterized and it belongs to only a handful of complexes having nitrito-bound mononuclear copper(II) centre. The metal atom has a distorted square pyramidal geometry with the copper atom displaced from the equatorial plane by 0.25 Å. In MeCN solution the green complex exhibits a broad ligand-field transition at 655 nm with a shoulder at 675 nm and in dichloromethane-toluene glass (80 K) it exhibits an EPR spectral feature characteristic of the unpaired electron in the dx2y2 orbital. Variable-temperature (80–300 K) magnetic susceptibility measurements in the solid state as well as room temperature measurement in MeCN solution reveal mononuclear magnetically dilute copper(II) centre. When examined by cyclic voltammetry (MeCN solution) it displays electrochemically irreversible CuII---CuI response [cathodic peak potential, Epc (V vs saturated calomel electrode (SCE)): −0.32]. An oxidative response is observed at 1.14 V, probably due to bound-nitrite oxidation and is partially removed to generate a solvated complex at the electrode surface. The latter species gives rise to reversible CuII---CuI redox response [ ].  相似文献   

16.
Cobalt(II) and copper(II) complexes with 1-allyl-2-methylimidazole (L), of general formula [ML2(NO3)2], have been prepared in the solid state. The compounds were characterised by structural, spectroscopic and magnetic measurements. The metal ions in both six coordinate complexes are surrounded by two nitrogen atoms of the imidazole rings and four oxygen atoms of the chelating nitrato group (the CoN2O4 and CuN2O4 chromophores). The structure of both chromophores is described by a very distorted tetragonal bipyramid. The formation of successive complexes of the azole with Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ in aqueous solution was followed potentiometrically. An irregularity in the Kn constants of successive Co2+ and Zn2+ complexes suggests a change in the coordination sphere of the central ions from octahedral to tetrahedral. With the Co2+–1-allyl-2-methylimidazole system, the change has been proven by inspection of the visible absorption spectra.  相似文献   

17.
Fourier Transform Infrared (FTIR), p-polarized grazing angle (GAIR) and Horizontal Attenuated Total Reflectance (HATR) spectra have been recorded of arachidic acid (AA)/1,2-bis(dodecyloxy)-4,5-diaminobenzene (DADB) Y-type alternate LB films deposited on an aluminium plate with 31 layers. It is well known that the frequencies of CH2 stretching bands of a hydrocarbon chain are sensitive to the conformational ordering of the chain. Changes in frequency and intensity can be used to characterize film ordering and preferential molecular packing. The observed peak frequencies and intensities of these bands indicate that the alkyl chains are present in a mostly trans conformation and tilted from the normal direction with respect to the substrate in LB films. The FTIR–GAIR and HATR spectra of 31 layers alternate film show significant changes in the region 1700–1400 cm−1 due to the partial proton transfer between acid and amine head groups. According to the HATR spectrum, the peak at 1731 cm−1 is observed due to a proportion of the carboxylic acid groups forming sideways dimers indicating that if the carboxylic acid groups form sideways dimers, they are less likely to undergo proton transfer with the amino groups.  相似文献   

18.
The 1:1 and 2:1 complexes between water and trans- and cis-isomers of nitrous acid have been isolated in argon matrices and studied using FTIR spectroscopy and DFT(B3LYP) calculations with a 6-311++G(2d,2p) basis set. The analysis of the experimental spectra indicate that 1:1 complexes trapped in solid argon involve very strong hydrogen bond in which acid acts as the proton donor and water as the proton acceptor. The perturbed OH stretches are −248, −228 cm−1 red shifted from their free-molecules values in complexes formed by trans- and cis-HONO isomers, respectively. The calculated spectral parameters for the two complexes are in good agreement with experimental data. The calculations also predict stability of two more 1:1 weakly bound complexes formed by each isomer. In these the water acts as the proton donor and one of the two oxygen atoms of the acid as the acceptor. The experimental spectra demonstrate also formation of 2:1 complex between water and trans-HONO isomer in an argon matrix. The performed calculations indicate that the complex involves a seven-membered ring in which OH group of HONO forms very strong hydrogen bond with the oxygen atom of one water molecule and nitrogen atom acts as a weak proton acceptor for the hydrogen atom of the second water molecule of the water dimer. The observed perturbations of the OH stretch of trans-HONO (750 cm−1 red shift) is much larger than that predicted by calculations (556 cm−1 red shift); this difference is attributed to strong solvation effect of argon matrix on very strong hydrogen bond.  相似文献   

19.
Fourier transform infrared spectra (4000–400 cm−1) are reported for metal(II) halide 4-vinlypridine complexes of the following stoichiometries: [MX2(4-vipy]n (n=4, M=Ni, X=Cl or Br; n=2, M=Cd, X=Cl, Br or I) and assignment are given for all the observed bands. These spectra were compared with X-ray powder diffraction patterns of complexes. It is shown that the proposed structures for these complexes derived from FTIR spectra are consistent with the X-ray powder diffraction measurements and the elemental analysis results. Coordination effect on 4-vinylpyridine has also been investigated.  相似文献   

20.
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.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号