FTIR and Ab Initio Studies of Diisopropylsulfoxide and its Solutions

Fourier transform infrared (FTIR) measurements, ab initio quantum chemical calculations at the restricted Hartree–Fock (RHF) level and density functional theory (DFT) calculations have been performed to study molecular interactions in pure diisopropylsulfoxide (DiPSO) and the binary mixtures DiPSO/CCl₄ and DiPSO/water. The optimized molecular geometry, vibrational wavenumbers, dipole moments and several thermodynamic parameters of free DiPSO and DiPSO/water 1:1 complex in the ground state were calculated using the RHF and B3LYP methods with the 6-31G(d) basis set. A fitting procedure has been performed for both SO and CH stretching regions and a detailed spectral interpretation has been done based on the data obtained from ab initio calculations, infrared spectra and band deconvolution analysis.     

Complexation of lanthanides(III), americium(III), and uranium(VI) with bitopic N,O ligands: an experimental and theoretical study

New functionalized terpyridine-diamide ligands were recently developed for the group actinide separation by solvent extraction. In order to acquire a better understanding of their coordination mode in solution, protonation and complexation of lanthanides(III), americium(III), and uranium(VI) with these bitopic N,O-bearing ligands were studied in homogeneous methanol/water conditions by experimental and theoretical approaches. UV-visible spectrophotometry was used to determine the protonation and stability constants of te-tpyda and dedp-tpyda. The conformations of free and protonated forms of te-tpyda were investigated using NMR and theoretical calculations. The introduction of amide functional groups on the terpyridine moiety improved the extracting properties of these new ligands by lowering their basicity and enhancing the stability of the corresponding 1:1 complexes with lanthanides(III). Coordination of these ligands was studied by density functional theory and molecular dynamics calculations, especially to evaluate potential participation of hard oxygen and soft nitrogen atoms in actinide coordination and to correlate with their affinity and selectivity. Two predominant inner-sphere coordination modes were found from the calculations: one mode where the cation is coordinated by the nitrogen atoms of the cavity and by the amide oxygen atoms and the other mode where the cation is only coordinated by the two amide oxygen atoms and by solvent molecules. Further simulations and analysis of UV-visible spectra using both coordination modes indicate that inner-sphere coordination with direct complexation of the three nitrogen and two oxygen atoms to the cation leads to the most likely species in a methanol/water solution.     

N-Salicylideneamino acidato complexes of oxovanadium(IV). The cysteine and penicillamine complexes

Oxovanadium(IV) complexes with ligands derived from the reaction of salicylaldehyde with L-cysteine and with D- and D,L-penicillamine are prepared. The compounds are characterised by elemental analysis, spectroscopy (UV-VIS, CD, EPR), TG, DSC and magnetic susceptibility measurements (9-295 K). We discuss several aspects related to the structure of these complexes in the solid state and in solution; in particular, the possibility of forming thiazolidine complexes, and their comparison with the characterised complexes is studied by molecular mechanics and density functional theory calculations. The solution structures depend on pH and solvent, and while with L-Cys the spectroscopic results show trends similar to those of the L-Ala and L-Ser systems up to ca. pH 8-9, where thiolate coordination starts being detected, the penicillamine system is quite distinct, namely thiolate coordination occurs for pH > 6.5. In the presence of salicylaldehyde and V(IV)O the desulfydration of cysteine proceeds rapidly, but no similar reaction occurs with penicillamine, although its decomposition is also activated. The DFT calculations do not indicate any energetic basis for this distinct reactivity, which possibly results from different complexes present in the Cys and Pen systems. In the cysteine system, the N-salicylidenedehydroalanine-V(IV)O complex V is believed to form in an intermediate stage of the desulfydration. Further, addition of several nucleophiles to the cysteine reaction mixtures produce amino acid derivatives by a Michael-type base-catalysed addition, a result compatible with the formation of V. The products of these reactions were analysed by TLC and HPLC, and in some cases isolated.     

双β-二酮配体配位性的理论研究

基于自洽反应场(SCRF)中的极化连续介质模型(PCM), 采用密度泛函理论B3LYP/6-31G**计算了以二硫醚和芳环为桥基的两类双β-二酮配体的空间构型和电子结构, 结合其配合物晶体结构数据, 研究配体分子电子结构与配位性的关联性. 结果表明, 配体分子的几何构型、前线轨道、偶极矩和电荷布居, 与配合物构型、活性配位原子和配位形式(单核或多核、分子内或分子间)之间的关联性与一致性十分有意义. 配体的理论计算研究可以在一定层次上为配合物几何结构特征和配位特性提供合理的分析与预测.     

Computational Bottom-up Design of Ytterbium(Ⅱ) Complex with Pyridyl Amido Ligand

Having been designed via bottom-up strategy based on density functional theory(DFT) calculations, a complex of ytterbium(Ⅱ) with pyridyl amido ligand was successfully synthesized by one-pot reaction in laboratory. DFT calculation shows that pyridyl amido ligands can stabilize the complex via steric and electron effect. This success in integrating computation with synthesis will inspire more explorations in the development of a new complex in lanthanide chemistry.     

D-penicillamine adsorption on gold: an in situ ATR-IR spectroscopic and QCM study

The adsorption of penicillamine from ethanol on gold was studied in situ by attenuated total reflection infrared (ATR-IR) and quartz crystal microbalance (QCM) experiments. Both ATR-IR and QCM reveal a fast mass uptake. In ethanol, the molecule adopts a zwitterionic form. Upon adsorption, part of the molecules deprotonate at the amine group, which is a relatively slow process that goes along with a strong shift of the nu(as)(COO(-)) mode. Both ATR-IR and QCM confirm a physisorbed layer. ATR-IR furthermore shows that the latter consists of zwitterionic molecules only, whereas both zwitterionic and anionic species are found in the chemisorbed layer. The infrared spectra of the physisorbed and chemisorbed layers are rather different, and the molecules within both layers seem to be oriented with respect to the surface. The ATR-IR spectra furthermore indicate that all three functional groups of penicillamine (i.e., thiol, carboxylate, and amine) interact with the surface, and density functional theory calculations support this finding. QCM also shows that the molecule uses considerably more space on the surface than molecules of similar size, which supports a three-point interaction. The latter leads to a strong anchoring of the molecule to the metal, which may explain the exceptional capability of penicillamine to bind metals.     

FT-IR,FT-Raman,ab initio and DFT structural and vibrational frequency analysis of 6-aminopenicillanic acid

Quantum mechanical calculations of energies, geometries and vibrational wavenumbers of 6-aminopenicillanic acid were carried out by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6-311G(d,p) basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with experimental X-ray data. A detailed interpretation of the infrared spectra has also been reported. The theoretical IR and Raman spectrograms have been constructed and compared with the experimental FT-IR and FT-Raman spectra. The differences between the observed and scaled wavenumber values of most of the fundamentals are very small. The thermodynamic parameters have also been computed.     

Insights into the structures, energetics, and vibrations of aqua-rubidium(I) complexes: ab initio study

We have carried out ab initio and density functional theory calculations of hydrated rubidium cations. The calculations involve a detailed evaluation of the structures, thermodynamic properties, and IR spectra of several plausible conformers of Rb+ (H2O)(n=1-8) clusters. An extensive search was made to find out the most stable conformers. Since the water-water interactions are important in hydrated Rb+ complexes, we investigated the vibrational frequency shifts of the OH stretching modes depending on the number of water molecules and the presence/absence of outer-shell water molecules. The predicted harmonic and anharmonic vibrational frequencies of the aqua-Rb+ clusters reflect the H-bonding signature, and would be used in experimental identification of the hydrated structures of Rb+ cation.     

Vibrational markers for the open-shell character of transition metal bis-dithiolenes: an infrared, resonance raman, and quantum chemical study

Transition metal complexes involving the benzene-1,2-dithiol (L(2-)) and Sellmann's 3,5-di-tert-butylbenzene-1,2-dithiol(L(Bu 2-)) ligands have been studied by UV-vis, infrared (IR), and resonance Raman (rR) spectroscopies. Raman spectra were obtained in resonance with the intervalence charge transfer (IVCT) bands in the near-infrared region and ligand-to-metal charge transfer (LMCT) bands in the near-UV region. Geometry optimization and frequency calculations using density functional theory (DFT) have been performed for [M(L)(2)](z) and [M(L(Bu))(2)](z) species (M = Ni, Pd, Pt, Co, Cu, Au, z = -1; M = Au, z = 0). On the basis of frequency calculations and normal-mode analysis, we have assigned the most important totally symmetric vibrations as well as corresponding overtone and combination bands that appear in rR spectra of compounds [Ni(L)(2)](1-), [M(L(Bu))(2)](1-) (M = Ni, Pt, Co, Cu). Experimental values of dimensionless normal coordinate displacements in excited states have been determined by fitting of rR spectra together with the absorption band shape, based on the time-dependent theory of Heller. Time-dependent density functional theory (TD-DFT) and multireference post-Hartree-Fock ab initio calculations, using the difference dedicated configuration interaction (MR-DDCI) method, were carried out to evaluate dimensionless normal coordinate displacements quantum chemically. The calculations show encouraging agreement with the experimental values. The large distortions along several normal modes led to significant vibronic broadening of IVCT and LMCT bands, and the broadening was accounted for in the deconvolution of the absorption spectra. The presence of an intense rR band around approximately 1100 cm(-1) was found to be a reliable marker for the presence of sulfur-based radicals.     

Structures, energetics, and spectra of aqua-cesium (I) complexes: an ab initio and experimental study

The design of cesium-selective ionophores must include the nature of cesium-water interactions. The authors have carried out extensive ab initio and density functional theory calculations of hydrated cesium cations to obtain reasonably accurate energetics, thermodynamic quantities, and IR spectra. An extensive search was made to find the most stable structures. Since water...water interactions are important in the aqua-Cs+ clusters, the authors investigated the vibrational frequency shifts as a function of the number of water molecules and the frequency characteristics with and without the presence of outer-shell water molecules. The predicted vibrational frequencies were then compared with the infrared photodissociation spectra of argon-tagged hydrated cesium cluster ions. This comparison allowed the identification of specific hydrogen-bonding structures present in the experimental spectra.     

Bonding interactions in oxydiacetate and thiodiacetate cobalt(II) and nickel(II) complexes

The influence of the central donor atom of the oxydiacetate and thiodiacetate ligands (oxygen and sulphur atoms, respectively) on the thermodynamic parameters for complexation reactions of the Co²⁺ and Ni²⁺ ions has been investigated using the isothermal titration calorimetry (ITC) technique and density functional theory (DFT) computations. The polarized continuum (PCM) - solvation model was employed to describe the structural factors that govern the coordination modes of the ligands (mer or fac) in the solution. The differences in the binding enthalpies of the investigated complexes were discussed based on the results obtained both from the natural bond orbital (NBO) analysis and the second-order perturbation theory.     

Photochemical electron transfer reactions of tirapazamine

The absorption and fluorescence spectra of 3-aminobenzo-1,2,4-triazine di-N-oxide (tirapazamine) have been recorded and exhibit a dependence on solvent that correlates with the Dimroth ET30 parameter. Time-dependent density functional theory calculations reveal that the transition of tirapazamine in the visible region is pi-->pi* in nature. The fluorescence lifetime is 98+/-2 ps in water. The fluorescence quantum yield is approximately 0.002 in water. The fluorescence of tirapazamine is efficiently quenched by electron donors via an electron-transfer process. Linear Stern-Volmer fluorescence quenching plots are observed with sodium azide, potassium thiocyanate, guanosine monophosphate and tryptophan (Trp) methyl ester hydrochloride. Guanosine monophosphate, tyrosine (Tyr) methyl ester hydrochloride and Trp methyl ester hydrochloride appear to quench the fluorescence at a rate greater than diffusion control implying that these substrates complex with tirapazamine in its ground state. This complexation was detected by absorption spectroscopy.     

Synthesis,characterization, crystal structure and DFT studies on 3-(1H-benzo[d][1,2,3]triazol-1-yl)-1-(4-ethylphenyl)-1-oxopropan-2-yl-4-ethylbenzoate

3-(1H-benzo[d][1,2,3]triazol-1-yl)-1-(4-ethylphenyl)-1-oxopropan-2-yl-4-ethyl-benzoate (BEOE) has been synthesized and characterized by elemental analysis, IR, UV–vis and fluorescence spectroscopy. Its crystal structure has also been determined by X-ray single crystal diffraction. For the title compound, density functional theory (DFT) calculations of the structure and vibrational frequencies have been performed at B3LYP/6-31G* level of theory. Based on the vibration analysis, thermodynamic properties of the title compound have been calculated. The correlative equations between the thermodynamic properties and temperatures have also been listed. By using TD-DFT method, electron spectra of the title compound have been predicted, which suggests the B3LYP/6-31G* method can approximately simulate the electron spectra for the system presented here.     

Complexation, computational, magnetic, and structural studies of the Maillard reaction product isomaltol including investigation of an uncommon π interaction with copper(II)

The metal complexation properties of the naturally occurring Maillard reaction product isomaltol HL(2) are investigated by measurement of its stability constants with copper(II), zinc(II), and iron(III) using potentiometric pH titrations in water, by structural and magnetic characterization of its crystalline complex, [Cu(L(2))(2)]·8H(2)O, and by density functional theory calculations. Strong complexation is observed to form the bis(isomaltolato)copper(II) complex incorporating copper in a typical (pseudo-)square-planar geometry. In the solid state, extensive intra- and intermolecular hydrogen bonding involving all three oxygen functions per ligand assembles the complexes into ribbons that interact to form two-dimensional arrays; further hydrogen bonds and π interactions between the furan moiety of the anionic ligands and adjacent copper(II) centers connect the complexes in the third dimension, leading to a compact polymeric three-dimensional (3D) arrangement. The latter interactions involving copper(II), which represent an underappreciated aspect of copper(II) chemistry, are compared to similar interactions present in other copper(II) 3D structures showing interactions with benzene molecules; the results indicate that dispersion forces dominate in the π system to chelated copper(II) ion interactions.     

Nonoxovanadium(IV) and oxovanadium(V) complexes with mixed O, X, O-donor ligands (X = S, Se, P, or PO)

Ligating properties of four potentially tridentate bisphenol ligands containing [O, X, O] donor atoms (X = S 1, Se 2, P 3, or P=O 4) toward the vanadium ions in +IV or +V oxidation states have been studied. Each ligand with different heterodonor atoms yields as expected nonoxovanadium(IV) complexes, V(IV)L(2), whose structures have been determined by X-ray diffraction methods as having six-coordinate V(IV), VO(4)X(2), core. Compounds 1-4 have also been studied with electrochemical methods, variable-temperature (2-295 K) magnetic susceptibility measurements, X-band electron paramagnetic resonance (EPR) (2-60 K) spectroscopy, and magnetic circular dichroism (MCD) (5 K) measurements. Electrochemical results suggest metal-centered oxidations to V(V) (i.e., no formation of phenoxyl radicals from the coordinated phenolates). A combination of density functional theory calculations and experimental EPR investigations indicates a dramatic effect of the heteroatoms on the electronic structure of 1-4 with consequent reordering of the energy levels; 1 and 3 possess a trigonal ground state (d(z)()(2))(1), but 4 with the phosphoryl oxygen as the heterodonor atom in contrast exhibits a tetragonal ground state, (d(xy)())(1). On the basis of the intense electronic transitions in absorption spectra, all electronic transitions observed for 4 have been assigned to ligand-to-metal charge-transfer transitions, which have been confirmed by preliminary resonance Raman measurements and C/D ratios obtained from low-temperature MCD spectroscopy. Moreover, diamagnetic complexes 5 and 6 containing mononuclear and dinuclear oxovanadium(V) units have also been synthesized and structurally and spectroscopically ((51)V NMR) characterized.     

Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with diethylenetriaminepentaacetic acid: temperature effect and coordination modes

Stability constants of two DTPA (diethylenetriaminepentaacetic acid) complexes with lanthanides (ML(2-) and MHL(-), where M stands for Nd and Eu and L stands for diethylenetriaminepentaacetate) at 10, 25, 40, 55, and 70 °C were determined by potentiometry, absorption spectrophotometry, and luminescence spectroscopy. The enthalpies of complexation at 25 °C were determined by microcalorimetry. Thermodynamic data show that the complexation of Nd(3+) and Eu(3+) with DTPA is weakened at higher temperatures, a 10-fold decrease in the stability constants of ML(2-) and MHL(-) as the temperature is increased from 10 to 70 °C. The effect of temperature is consistent with the exothermic enthalpy of complexation directly measured by microcalorimetry. Results by luminescence spectroscopy and density functional theory (DFT) calculations suggest that DTPA is octa-dentate in both the EuL(2-) and EuHL(-) complexes and, for the first time, the coordination mode in the EuHL(-) complex was clarified by integration of the experimental data and DFT calculations. In the EuHL(-) complex, the Eu is coordinated by an octa-dentate H(DTPA) ligand and a water molecule, and the protonation occurs on the oxygen of a carboxylate group.     

Microsolvation effects on the optical properties of crystal violet

We present a joint experimental and theoretical study of the photoabsorption and photodissociation behavior of crystal violet, that is, the tris[p-(dimethylamino)phenyl]methyl cation. The photodissociation spectra of isolated and microsolvated crystal violet have been measured. A single band is observed for the bare cation. This is in good agreement with the calculated vibronic absorption spectrum based on time-dependent density functional theory calculations. The interaction of crystal violet with a single water molecule shifts and broadens the photodissociation spectrum, so that it approaches the spectrum obtained in solution. Theoretical calculations of the structure of the complex suggest that the shift in the absorption spectrum originates from a water molecule bonding with the central carbon atom of crystal violet.     

原位水热合成的二(2,4-二(对硝基苯)-1,3,5-环戊二烯铜配合物的实验和理论研究

以4-硝基对苯腈,氨水和铜盐反应于在原位水热条件下合成了二（2,4-二（对硝基苯）-1,3,5-环戊二烯铜配合物,通过单晶X射线衍射,元素分析,红外,核磁光谱和热重分析等手段对其进行了表征。结构分析表明,铜与四个源自原位合成的配体上的氮原子配位形成平面四边形构型。基于密度泛函的理论计算对配合物的热力学稳定性进行了阐释。