Synthesis and vibrational study of platinum(II) and palladium(II) complexes of glyoxilic acid oxime

New platinum(II) and palladium(II) complexes of glyoxilic acid oxime (gao) have been prepared and characterised by infrared (4000–150 cm⁻¹) and Raman (4000–200 cm⁻¹) spectra. The gao acts as bidentate ligand bonding through the oxime nitrogen and carboxyl oxygen atoms to form neutral bis-chelate square-planar complexes. The lowest energy conformer of the gao ligand (ectt) was selected among 16 theoretically possible conformers on the basis of ab initio calculations at HF/3-21G*, HF/6-31G* and HF/6-311** levels of the theory from which structural parameters and conformational stabilities have been obtained. A complete vibrational assignment of the gao was performed for the lowest energy ectt conformer on the basis of ab initio optimised parameters and normal coordinate analysis calculations (PED). NCA calculations of the complexes studied were also performed.     

The performance of different density functional methods in the calculation of molecular structures and vibrational spectra of platinum(II) antitumor drugs: cisplatin and carboplatin

A comparison of eight density functional models for predicting the molecular structures, vibrational frequencies, infrared intensities, and Raman scattering activities of platinum(II) antitumor drugs, cisplatin and carboplatin, is reported. Methods examined include the pure density functional protocols (G96LYP, G96PW91, modified mPWPW and original PW91PW91), one‐parameter hybrid approaches (mPW1PW and mPW1LYP), and three‐parameter hybrid models (B3LYP and B3PW91), as well as the HF and MP2 levels of theory. Different effective core potentials (ECPs) and several basis sets are considered. The theoretical results are discussed and compared with the experimental data. It is remarkable that the mPW1PW protocol introduced by Adamo and Barone [J Chem Phys 1998, 108, 664], is clearly superior to all the remaining density functional methods (including B3LYP). The geometry and vibrational frequencies of cisplatin and carboplatin calculated with the mPW1PW method, and the ECP of Hay and Wadt (LanL2DZ basis set) are in better agreement with experiment than those obtained with the MP2 method. The use of more elaborated ECP and the enlargements of basis sets do not significantly improve the results. A clear‐cut assignments of the platinum‐ligand vibrations in cisplatin and carboplatin are presented. It is concluded that mPW1PW is the new reliable method, which can be used in predicting molecular structures and vibrational spectra of large coordination compounds containing platinum(II). © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 901–912, 2001     

DFT and experimental studies of the structure and vibrational spectra of curcumin

The potential energy surface of curcumin [1,7‐bis(4‐hydroxy‐3‐methoxyphenyl)‐1,6‐heptadiene‐3,5‐dione] was explored with the DFT correlation functional B3LYP method using 6‐311G* basis. The single‐point calculations were performed at levels up to B3LYP/6‐311++G**//B3LYP/6‐311G*. All isomers were located and relative energies determined. According to the calculation the planar enol form is more stable than the nonplanar diketo form. The results of the optimized molecular structure are presented and compared with the experimental X‐ray diffraction. In addition, harmonic vibrational frequencies of the molecule were evaluated theoretically using B3LYP density functional methods. The computed vibrational frequencies were used to determine the types of molecular motions associated with each of the experimental bands observed. Our vibrational data show that in both the solid state and in all studied solutions curcumin exists in the enol form. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Rhodium(III), palladium(II) and platinum(II) complexes of Bis(o-aminobenzenesulfonyl)ethylenediamine

New complexes of the formulae K₃[RhL ₃]·2 H₂O, [PdL]·H₂O and [M(LH₂)Cl₂] [whereM = Pd, Pt andLH₂ = bis(o-aminobenzenesulfonyl)ethylenediamine] have been prepared and characterized by conductivity measurements, thermogravimetric analysis, X-ray powder patterns and IR, Ligand Field and¹H-NMR spectroscopy.

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Rhodium(III), Palladium(II)- und Platin(II)-Komplexe mit Bis(o-aminobenzolosulfonyl)ethylendiamin (Kurze Mitteilung)

Zusammenfassung Neue Komplexe der allgemeinen Formeln K₃[RhL ₃]·2H₂O, [PdL]·H₂O und [M(LH₂)Cl₂] mitM = Pd, Pt undLH₂ = Bis(o-aminobenzolosulfonyl)ethylendiamin wurden dargestellt und mit Konduktionsmessungen, thermogravimetrischen Analysen, Röntgenstrukturanalysen, IR, Ligandfeld- und¹H-NMR-Spektroskopie charakterisiert.

     

Density functional theory study of vibrational spectra. 8. Assignment of fundamental vibrational modes of 9,10-anthraquinone and 9,10-anthraquinone-d8

Density functional theory (using Becke's exchange and Lee-Yang-Parr's correlation functionals (BLYP)) and ab initio Hartree-Fock calculations were carried out in order to investigate the molecular structure and vibrational spectra of 9,10-anthraquinone and its perdeuterated analog. The calculated structural and spectral features are in good agreement with the available experimental results. Most of the BLYP/6-31G* non-CH(D) stretching frequencies are slightly lower than reliable experimental assignments; the mean absolute deviation is about 14 cm⁻¹. On the basis of agreement between calculated and experimental results, assignments of the fundamental vibrational modes were examined and some reassignments were proposed. The calculated results can serve as a guide for a future experimental search for the missing fundamentals of the target molecules.     

X-ray crystal structure and vibrational spectra of hydrazides and their metal complexes. Part II. Hexaaquacobalt(II)bis(phthalhydrazidato)tetrahydrate

The hexaaquacobalt(II)bis(phthalhydrazidato)tetrahydrate, [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O is examined using single crystal X-ray diffraction analysis. The crystals are triclinic, space group , with a = 9.757(1), b = 10.955(2), c = 11.106(1),  = 100.79(2), β = 90.35(3), γ = 91.54(1) and Z = 2. In [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O, the cobalt(II) is coordinated by six water ligands and the [Co(H₂O)₆]²⁺ is associated with the two O-deprotonated phthalhydrazidato ions only by hydrogen bonds. The infrared and Raman spectra of phthalhydrazide (PH) and infrared spectra of deuterated derivative phthalhydrazide (PD) and of [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O are reported. The theoretical wavenumbers, infrared intensities and Raman scattering activities have been calculated using density functional (B3LYP) method with the 6-311++G(d,p) basis set. The calculated potential energy distribution has proved to be of great help in assigning the spectra PH, its deuterated derivative and [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O. The results from natural bond orbital (NBO) analysis for keto-hydroxy form of PH are presented.     

Unusual co-ordination behaviour of imidazole-4-acetic acid. Synthesis, crystal structure and vibrational studies of one-dimensional co-ordination polymer of zinc(II) with two different ligand forms

This work is devoted to structural and vibrational studies of novel 1D polymeric zinc(II) complex [ZnCl(ia)(Hia)]·H₂O (infinity) [Hia=imidazole-4-acetic acid]. It has been found for the first time that the ia anion is acting as bidentate bridging ligand with N1 and carboxylate oxygen atoms as binding centres. The quasi-tetrahedral coordination polyhedron is completed by one chloride anion and monodentate Hia ligand bonded with zinc(II) cation via carboxylate oxygen atom. The compound crystallise in the triclinic P space group with Z=2. The polymer chains are held together by hydrogen bonding network involving the N---H and carboxylate groups, chloride ions and water molecules. The differences between normal vibrations of two ligand forms present in the complex are discussed on the basis of the density functional calculations (DFT) performed for natural and N-deuterated isotopomers. The assignment of the observed MIR and Raman bands is given in terms of potential energy distribution (PED).     

DFT study on the intermolecular interactions between Aun (n = 2–4) and thymine

Density functional B3LYP method with 6-31++G** basis set is applied to optimize the geometries of the luteolin, water and luteolin–(H₂O)_n complexes. The vibrational frequencies are also studied at the same level to analyze these complexes. We obtained four steady luteolin–H₂O, nine steady luteolin–(H₂O)₂ and ten steady luteolin–(H₂O)₃, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) are used to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are within −13.7 to −82.5 kJ/mol. The strong hydrogen bonding mainly contribute to the interaction energies, Natural bond orbital analysis is performed to reveal the origin of the interaction. All calculations also indicate that there are strong hydrogen bonding interactions in luteolin–(H₂O)_n complexes. The OH stretching modes of complexes are red-shifted relative to those of the monomer.     

Synthesis and characterization of platinum(II) complexes with 2-imidazolidinethione. X-ray crystal structure of tetra(2-imidazolidinethione- S )platinum(II) iodide dimethylsulfoxide solvate monohydrate

Preparations of trans-[PtX₂(Imt)₂] (Imt =?2-imidazolidinethione, X=Cl^? or I^?) and [Pt(Imt)₄]I₂ are described. These complexes were characterized by elemental analysis, thermal analysis, mid- and far-IR spectroscopy, and NMR (¹H and ¹³C) spectroscopy. The crystal and molecular structure of [Pt(Imt)₄]I₂ ·?DMSO ·?H₂O was determined by X-ray diffraction methods. The structural data reveal the following features: (a) the platinum atom in [Pt(Imt)₄]²⁺ is essentially in a square-planar environment, (b) the entire dication possesses approximately C _2h symmetry, (c) no appreciable hydrogen bonding exists between the iodide ions and the Imt ligands in the dication, (d) two pairs of two mutually cis Imt ligands are arranged above and below the PtS₄ plane, respectively, and (e) two planes defined by two trans Imt rings are perpendicular to each other.     

Experimental and computational studies of the structure and vibrational spectra of 2-[5,5-dimethyl-3-(2-phenyl-vinil)-cyclohex-2-enylidene]-malononitrile

The FTIR spectra (4000-100 cm(-1)) and Raman spectra (3500-30 cm(-1)) of 2-[5,5-dimethyl-3-(2-phenyl-vinil)-cyclohex-2-enylidene]-malononitrile in solid state were measured. In addition, the structure and harmonic vibrational frequencies of this molecule were theoretically evaluated using B3LYP density functional methods. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Bond length alternation (BLA) was established. Comparison with the experimental spectra provides important information about the ability of this computational method to describe the vibrational modes in this type of "push-pull" systems with potential non-linear optical applications.     

DFT study of the structure and spectral behavior of new pt(II) complexes with 5‐methyl‐5(4‐pyridyl)hydantoin

Platinum complexes are a great interest of study, because of the antitumor activity and the clinical use of some of them in the recent anticancer chemotherapy. In many cases, computational studies can be very useful for predicting the structure and some physicochemical properties of metal complexes. Theoretical calculations can also be used for the rational design of new complexes with optimal ratio: antitumor activity/toxicity. The geometry of three new Pt(II) complexes with general formula cis‐[PtL₂X₂] (where L is 5‐methyl‐5(4‐pyridyl)hydantoin and X = Cl^?, Br^?, I^?) and of the free organic ligand were optimized using the hybrid DFT method B3LYP with LAN2DZ basis sets. The results were in very good correlation with the data of similar compounds from the literature. The same DFT method was used for the study of their spectral behavior, by reproducing their IR and Raman spectra and comparing them with experimental data. In addition, the distribution of charges by ESP analysis was calculated. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

N(4)-tolyl-2-benzoylpyridine-derived thiosemicarbazones and their palladium(II) and platinum(II) complexes: Cytotoxicity against human solid tumor cells

Complexes [Pt(2Bz4oT)Cl], [Pt(2Bz4mT)Cl], and [Pt(2Bz4pT)Cl] were prepared with N(4)-ortho-(H2Bz4oT), N(4)-meta-(H2Bz4mT), and N(4)-para-(H2Bz4pT) tolyl-2-benzoylpyridine-derived thiosemicarbazones. The thiosemicarbazones exhibited moderate anti-proliferative activity against HepG2 (hepatoma) and UACC-62 (melanoma) cancer cell lines, but showed high anti-proliferative effect against A431 (epithelial carcinoma) cancer cell lines. Upon coordination to platinum(II) the anti-proliferative activity decreases in all cases. The cytotoxicity of the previously prepared palladium(II) analogues [Pd(2Bz4oT)Cl], [Pd(2Bz4mT)Cl], and [Pd(2Bz4pT)Cl] was also investigated. As in the case of the platinum(II) complexes, coordination to palladium(II) did not lead to activity improvement. Investigations on the mechanism of cytotoxic action against A431 cells revealed that [Pd(2Bz4oT)Cl] induced DNA fragmentation and apoptosis while H2Bz4oT did not present this effect. The high anti-proliferative effect of the thiosemicarbazones and [Pd(2Bz4oT)Cl] against A431 cells, together with the pro-apoptotic effect of [Pd(2Bz4oT)Cl] suggests that these compounds have potential as chemotherapeutic drug candidates.     

X-ray crystal structures of novel platinum(II) and palladium(II) complexes of dialkyl phosphonated phosphines

Two diethyl phosphonated phosphine ligands of formula Ph₂P(CH₂)₃PO₃Et₂ (ligand L) and Ph₂P(4-C₆H₄PO₃Et₂) (ligand L′) were used to prepare different complexes of platinum(II) (1, cis-PtCl₂L₂; 2, trans-PtCl₂L₂·H₂O; 3A and 3B, cis- and trans-PtCl₂L′₂) and palladium(II) (4, [PdCl₂L]₂; 5, trans-PdCl₂L₂·H₂O; 6, trans-PdCl₂L′₂·CH₂Cl₂). The single-crystal X-ray structure analyses of complexes 1, 2, 4-6 indicate that complexation involved only the phosphine end, whereas the strong polarization of the PO bond was highlighted by the formation of hydrogen bonds with a water molecule in 2 and 5, and with a dichloromethane molecule in 6, with an exceptionally short CH?O hydrogen bond length (C?O separation 3.094(3) Å).     

Infrared and Raman spectra,DFT investigation of the tautomerism,conformational equilibrium,structure and vibrational assignment of 1-(2-benzothiazolyl)-3-methyl pyrazol-5-one

The low energy conformations of the three tautomers, imine-enol, enamine-keto and imine-keto forms of the title compound have been determined at the B3LYP/6-31 + G(d) level of theory using the relaxed PES scan method and their geometries have been refined at B3LYP/6-311 + G(d,p) and PBE0/6-311 + G(d,p) levels. The results show that the title compound exists in the imine-enol tautomeric form, in contrast to the enamine-keto form which exists in the solid crystalline state, followed by enamine-keto and imine-keto forms with extremely low abundances. The geometry parameters of all tautomeric forms calculated at PBE0/6-311 + G(d,p) and B3LYP/6-311 + G(d,p) levels have been compared with those from the experimental X-ray diffraction. The vibrational (FT-IR and Raman) spectroscopic studies of the most stable tautomer, enamine-keto form have been carried out. The assignment of the fundamental bands observed in the IR and Raman spectra have been facilitated by the SQM force field procedure. The frequencies from SQM procedure have a very good fit to the experimental ones. The total root-mean-square error is only ca. 11 cm⁻¹.     

Synthesis and characterization of new platinum(II) phosphinate complexes

The syntheses of platinum(II) complexes of bis(dimethylphosphinylmethylene)amine and bis(aminomethyl)phosphinic acid were investigated. In the case of bis(dimethyl-phosphinylmethylene)amine the reaction with K₂[PtCl₄] yields the potassium amino-trichloroplatinate K[PtCl₃L] (L?=?bis(dimethylphosphinylmethylene)amine), which was characterized by multinuclear (¹H, ¹³C, ³¹P, and ¹⁹⁵Pt) NMR spectroscopy in solution. Bis(aminomethyl)phosphinic acid reacts with K₂[PtCl₄] under strictly controlled pH conditions to give colorless crystals of the cisplatin analog K[PtCl₂L′] (L′?=?bis(aminomethyl)phosphinate). This complex was characterized by multinuclear NMR spectroscopy in solution as well as by single-crystal X-ray diffraction in the solid state. The bis(aminomethyl)phosphinate coordinates to platinum via both amino functions, thus acting as a chelating ligand.     

Ab initio study of 1,1-(methylphosphinylidene) bis(methanamine) and vibrational assignment of its N,N′-coordinated Pt(II) and Pd(II) chloro complexes

Infrared and Raman spectra of 1,1-(methylphosphinylidene) bis(methanamine) [mpbm, (CH₃)PO(CH₂NH₂)₂] and its N,N′-coordinated Pt(II) and Pd(II) have been studied in the 4000–200 cm⁻¹ frequency range. Ab initio calculations have been carried out for different conformations of the mpbm at HF/6-31G* level of the theory from which structural parameters, conformational stability and predicted infrared and Raman spectra have been obtained. A complete vibrational assignment of the lowest energy conformer, tttg⁻, as well as of its N,N′-coordinated Pt(II) and Pd(II) chloro-complexes was done on the basis of the calculated frequencies, relative infrared intensities, Raman activities and potential energy distribution (PED). The theoretical predictions are compared with the experimental results where appropriate.     

Copper(II), palladium(II) and platinum(II) chloride complexes with 5-amino-2-tert-butyltetrazole: Synthesis, characterization and cytotoxicity

Complexes CuL₃Cl₂, PdL₂Cl₂ and PtL₂Cl₂, where L is a novel ligand from the series of 2-substituted 5-aminotetrazoles, namely 5-amino-2-tert-butyltetrazole (1), have been synthesized by the reaction of metal(II) chlorides with 1 and characterized by IR spectroscopy, thermal and X-ray analyses. The crystallographic structural analysis of these complexes revealed that 1 acts as a monodentate ligand coordinated to the metal via endocyclic N4 atom. Platinum complex demonstrates promising cytotoxicity against human cervical carcinoma cells with IC₅₀ value average between those of cisplatin and carboplatin.     

Novel complexes of tris(aminomethyl)phosphanes with platinum(II): Structural, spectroscopic, DFT and biological activity studies

Two new platinum(II) complexes with tris(aminomethyl)phosphanes: [trans-PtCl₂{P(CH₂N(CH₂CH₂)₂NCH₃)₃}₂] (1Pt) and [trans-PtCl₂{P(CH₂N(CH₂CH₂)₂O)₃}₂] (2Pt) were prepared and characterized with NMR and UV-Vis spectroscopies. Their structures were investigated by X-ray crystallography and DFT methods. TDDFT calculations were employed to interpret the electronic spectra of the complexes. Obtained results are not unequivocal, however population analysis indicate, that the character of HOMO and HOMO−1 orbitals depend strongly on the electron donoring properties of the phosphane ligand. Biological activity of 2Pt complex, which is more stable and more soluble in polar solvents than 1Pt, was examined in vitro on the Vero cell line (IC₅₀ = 12.5 μM). At higher concentrations it induces apoptosis, probably due to changes of the cell cytoskeleton. Luminescence quenching studies and CD spectroscopy of interactions of 2Pt with HSA and BSA indicate that these albumins bind the complex slightly - without altering their tertiary structures, however HSA interacts with 2Pt noticeably stronger than BSA. It was also found that 2Pt does not cleave supercoiled pUC18 plasmid.