Atomic structure of the copper bromide complex based on benzoin 1′-phthalazinylhydrazone: DFT and X-ray absorption spectroscopy analysis

A copper bromide complex based on benzoin 1′-phthalazinylhydrazone is synthesized. Within density functional theory (OPBE/TZP) the optimal structural parameters of the complex are determined. X-ray Absorption Near-Edge Structure (XANES) spectra above the K absorption edge of copper are measured in the copper bromide complex. Theoretical XANES spectra of the K absorption edge of copper are calculated based on the full multiple scattering method and in the full potential of the finite difference method. Good agreement between the theoretical XANES spectrum and the experimental data is obtained.     

Biophysical and biochemical investigation on the binding of a manganese–cyanonitrosyl complex with DNA

The interaction of a cyanonitrosyl–manganate complex with DNA has been studied by u.v.–vis spectroscopy, circular dichroism, fluorescence and gel electrophoresis techniques. As the DNA 260 nm band remained insensitive to interaction, the interaction ratio was determined by monitoring the CN⁻→ Mn LMCT band observed at 222 nm, and the interaction ratio was found to be in the complex (D): DNA (P)=1:0.30 from the spectrophotometric titration. The above-mentioned physical measurements indicate that the binding mode is not intercalative and the cyanonitrosyl system is a groove binder.     

Aspects of acyclic azine chemistry—I. The effect of structure and solvents on the electronic absorption spectra of benzaldazine,o-, m- and p-hydroxybenzaldazines

The electronic absorption spectra of benzaldazine, o-, m-, and p-hydroxybenzaldazines have been separately examined in various solvents (20 solvents and solvent mixtures). The observed three groups of bands designated as α (200–225 nm), β (289–307 nm) and γ (352–375 nm) are attributed to π*←π transitions although experimental evidence based on spectra obtained in concentrated sulphuric acid reveals that π*←σ(n) transitions constitute part of the γ-band. On the basis of group theoretic analysis, in the singlet manifold, all π*←σ(n) transitions (i.e. ¹A_u ← 1¹A_g) are out-of-plane (z) polarized while all π*←π transitions (i.e. ¹B_u ← 1¹A_g are in-plane (x, y) polarized. In the rationalization of data, the theory of resonance has been employed where deemed useful. The shifts of bands with solvents have been traced.     

Magnetic,spectroscopic and biological properties of copper(II) complexes of the tridentate ligand, α-N-methyl-S-methyl-β-N-(2-pyridyl)methylenedithiocarbazate(NNS) and the X-ray crystal structure of the [Cu(NNS)I2] complex

Copper(II) complexes of general formula, Cu(NNS)X ₂ · nH₂O (NNS = the 2-formylpyridine Schiff base of N-methyl-S-methyldithiocarbazate; X = Cl^–, Br^–, I^–, NCS^–; n = 0, 2) have been synthesized and characterized by elemental analysis and by magnetic and spectroscopic techniques. Based on magnetic and spectroscopic data, a monomeric five-coordinate square-pyramidal structure is assigned to these complexes. The crystal and molecular structure of [Cu(NNS)I₂] has been determined by X-ray diffraction. The complex has a monomeric square-pyramidal structure with the ligand coordinated to the copper(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thione sulfur atom. The fourth and fifth coordination sites are occupied by the iodide ligands. Antimicrobial tests indicate that Schiff base is inactive against the bacteria, Bacillus subtilis (mutant defective DNA repair), Pseudomonas aeruginosa, methicillin resistant Staphylococcus aureus and Bacillus subtilis (wild type) and weakly active against the fungi, Candida albicans, Candida lypolytica, Saccharomyces cereviseae and Aspergillus ochraceous but its copper(II) complexes, Cu(NNS)X ₂ are strongly active against these organisms. A cytotoxicity study of the compounds against leukemic and cervical cancer cells showed that the Schiff base is inactive, but the complexes, [Cu(NNS)I₂] and [Cu(NNS)(NCS)₂] · 2H₂O exhibit significant activity against cervical cancer cells with CD₅₀ values of 4.8 and 4.2 g, respectively.     

Vibronic intensities in the electronic spectra of transition metal complex ions VIII: Vibrational coordinates for octahedral ions and their application to the4 A 2g ↔2 E g transition of the MnF 6 2− ion

Summary A reexamination of the vibrational coordinates appropriate in vibronic intensity calculations in octahedral coordination compounds is presented. We derive a complete set of symmetry coordinates that is orthonormal and transforms correctly under the group generators. The vibronic hamiltonian for the crystal field and ligand polarization contributions to the intensity are calculated in the basis of these coordinates. The crystal field term is evaluated both using a truncated basis set for the intermediate electronic states and using the closure approximation. These methods have been applied to the calculation of the vibronic intensity distribution for the⁴ A _2g ² E _g transition of the MnF ₆ ^2– ion and close agreement wtih experiment achieved.     

Molecular and supramolecular properties of a Hg(II) complex with (E)-N,N′-bis(2-pyridyl)iminoisoindoline: synthesis,spectroscopy, X-ray structure and Hirshfeld surface analyses,and DFT calculations

A scarcity of metal complexes containing (E)-N,N′-bis(heteroaryl)iminoisoindolines has prompted us to investigate the coordinating ability and supramolecular behavior of (E)-N,N′-bis(2-pyridyl)iminoisoindoline (2-pyimiso), a versatile iminobis(pyridyl) ligand. The 1:1 reaction of HgCl₂ with 2-pyimiso in MeOH afforded a dinuclear complex, [{HgCl(2-pyimiso)}₂(μ-Cl)₂] (1). The complex has been characterized by elemental microanalysis, vibrational spectroscopy (FTIR and FT-Raman) and ¹H NMR spectroscopy. DFT calculations at the B3LYP-D3/LACV3P** level have been used in support of our vibrational analysis. Single-crystal X-ray diffraction data have shown that the coordination geometry of 1 is intermediate between the trigonal pyramidal and seesaw shapes insofar as each Hg(II) is four-coordinate and 2-pyimiso is a monodentate ligand. X-ray structure and Hirshfeld surface analyses have revealed that the supramolecular arrangement of 1 comprises perpendicular 1-D chains along the [011] direction assembled by nonclassical C–H?Cl–Hg and C–H?π hydrogen bonds. Moreover, adjacent sheets parallel to the bc-plane are interconnected by C–H?N_py, π–π_py stacking, and Hg?π_py interactions.     

Investigation on the potential barrier to internal rotation in molecules——Ab initio calculation and energy partition of the internal rotation barrier in complex molecule H_3N-BH_3

Based on the ab initio/6-31G~* calculation, the potential barrier to internal rotation in mol-ecule H_3N--BH_3 has been studed by means of PD/LSF atomic charge model and Buckingham(exp--6-1)energy partition method. The results indicate that the order of the contributions of the componentsto the total energy barrier △E is |△V_(es)|(electrostatic) >|△V_(et)| (charge transfer)>|△V_(ex)| (exchangerepulsion)>|△V_(di)| (dispersion). For △V_(es) there are maxima at θ= 30°and 90°, and a saddle atθ= 60°. There are good linear relationships for the total barrier △E, △V_(ex) and △V_(di) with cos3θrespectively, and the same for the dipole moment from PD/LSF model (μ_(PD)) and that from abinitio calculation (μ_(QM)) vs. cos3θ respectively.