Properties Of Molecular Complexes Research Articles

Long-range dispersion-corrected density functional for noncovalent interactions

Noncovalent interactions are important in determining structures and properties of molecular complexes and biological molecules, and for understanding adsorption processes in chemistry and biological science, and are still challenging to conventional density functional theories. In this work, the recently developed Tao-Mo (TM) meta-GGA (generalized gradient approximation) functional is combined with the D3 scheme of long-range van der Waals (vdW) interaction correction and the parameters of damping function are optimized with the S66[Formula: see text]×[Formula: see text]8 set. The resulting TM-D3 method is applied to the medium-sized molecular set S22 and large size molecular complexes set L7 to calculate intramolecular interaction energies. The TM-D3 method produces the best accuracy for the S22 set with a MAE of 0.2 kcal/mol, improving upon the PBE-D3 (MAE[Formula: see text]=[Formula: see text]0.5 kcal/mol), PBE0-D3 (MAE[Formula: see text]=[Formula: see text]0.5 kcal/mol), TPSS-D3 (MAE[Formula: see text]=[Formula: see text]0.4 kcal/mol), M06L (MAE[Formula: see text]=[Formula: see text]0.8 kcal/mol), and SCAN-D3 (MAE[Formula: see text]=[Formula: see text]0.4 kcal/mol) methods. For the large size set L7, the TM-D3 (MAE[Formula: see text]=[Formula: see text]2.1 kcal/mol) also performs better than the PBE-D3 (MAE[Formula: see text]=[Formula: see text]2.6 kcal/mol), SCAN-D3 (2.5 kcal/mol) and M06L (3.0 kcal/mol), but not accurate than the PBE0-D3 (MAE[Formula: see text]=[Formula: see text]0.8 kcal/mol) and TPSS-D3 (MAE[Formula: see text]=[Formula: see text]1.1 kcal/mol). However, overall, the TM-D3 method performs very well with an error of 2.7% of mean binding of the S22 set and an error of 12.6% of the mean binding of the L7 set for the two typical and important medium and large size molecular complex sets. The success of the dispersion-corrected TM functional benefits from the ability of the plain TM functional to capture the short-range vdW interaction or extend the short-range interaction to the middle range, and the right coupling between the TM and the long-range vdW correction D3 scheme, leading to the improved description of noncovalent interactions.

Formation of Color Centers and Molecular Complexes with a Weak Hydrogen Bond in Lithium Fluoride Crystals Depending on the Form of OH¯ Inclusion

The form of oxygen-containing inclusions in the LiF crystal was shown to be determined by the laws of isomorphic substitution and impurity accumulation in a melt during crystal growth in open air. Color centers and hydrogen-bonded complexes of different types appear in the LiF crystal after irradiation depending on the form of OH– and Mg2+ inclusions. The radiative decay of OH– ions and the properties of molecular complexes (MCs) with a weak hydrogen bond are responsible for the decreased efficiency of formation of the F- and F2-color centers and increased concentration of the positively charged F 2 + - and F 3 + -centers. Radiochemical reactions involving hydrogen and fluorine atoms and ions that compete with the formation of color centers were presented.

Molecular Complexes of p-Chloranil with Aniline, Phenol and their Derivatives

Classification of simple supramolecular structures (for example molecular complexes), which has been introduced and described by Mulliken [1], is based on types of molecular orbitals of the components. In the paper [2], disadvantages of such classification are shown, which motivate us to return to the re-examination properties of molecular complexes. By this reason, there is a need to research the molecular complexes of one electron acceptor with a wide range of electron donor molecules. This paper have continued work (Part I [3]) on the chloranil complexes by studying the spectral properties complexes of N- and O-unsubstituting anilines and phenols. The present work aimed at analyzing linear relation the energies of charge-transfer bands of molecular complexes are related to ionization potentials of the donor components. All complexes conform to linear relations like involving both adiabatic and vertical ionization potentials of donor components. Mulliken [1] has been proposed to apply the vertical ionization potentials of donor components only. The development of photoelectron spectroscopy has led to the measurement of adiabatic and vertical ionization energies for thousands of molecules, which allow theirs to the present analysis of spectral properties molecular complexes.

A STUDY OF THE STRUCTURES AND VIBRATIONAL SPECTRA OF THE N2O⋯(HX)2 AND ON2⋯(HX)2 WITH X = F, Cl, Br AND CN

Theoretical calculations 6-311++G(d,p) have been performed in order to obtain binding energies and molecular properties of complexes involving nitrous oxide ( N2O ) and two HX (X = F, Cl, Br and CN ) molecules. Our calculations have revealed the existence of eleven stable structures. The vibrational changes which take place in the HX acid after complexation follow the usual behavior: the HX stretching frequency is shifted downward whereas its IR intensity is much enhanced. The new vibrational modes arising upon H-bond formation, were verified, especially, those associated with the out-of-plane and in-plane HX bending modes, which are pure rotations in the HX isolated molecule.

Conformational analysis of 2-methyl-1,3,2-dioxaborinane in the presence of an ammonia molecule

Nonempirical quantum chemical methods RHF//STO-3G, 3-21G and 6-31G(d) were used for the investigation of the conformational properties of molecular complexes of 2-methyl-1,3,2-dioxaborinane with ammonia (1:1). Two types of possible associates are revealed: with donor-acceptor N→B bond and with intermolecular NH···O hydrogen bond. Their calculated relative stability and conformational behavior are determined not only by the spatial orientation of the donor and the acceptor but also by the concepts of the used calculation approach.

Effect of steric strains in the macroring on the structure and properties of molecular complexes of (chloro)[5,15-(p-butoxyphenyl)-2,8,12,17-tetramethyl-3,7,13,17-tetrabutylporphinato]aluminum

The chelate (Cl)AlP was prepared by complexation of porphine (P) with aluminum(III) chloride in refluxing pyridine. Equilibrium coordination of nitrogen-containing ligands (L = 2-methylimidazole, imidazole, pyridine, 3,5-dimethylpyrazole, dimethylformamide) with (Cl)AlP in benzene was studied by spectrophotometric titration and computer simulation. Quantitative and qualitative characteristics of the reaction were obtained. The structure of the mixed-ligand complex formed by intermolecular interaction of the metal porphyrin with a base was determined spectrophotometrically and by quantum-chemical calculations. An effect of additional molecular ligand and of steric strain in the macroring on the stability of the complex was noted. The stability constant (Ks) increases with an increase in the basicity (KBH+) of the extra ligand and is proportional to the shift of the main bands (†λ) in the electronic absorption spectra. The geometric and energy characteristics of hexacoordinated aluminum porphyrin were calculated by the PM3 method. Correlations were found between the calculated energy of the interaction of the aluminum atom with the base molecule (Eb) and stability of the mixed-ligand complexes (Cl)Al(L)P. The cis and trans effects in the complexes (Cl)Al(L)P were analyzed. The dependence of the strength of the Al-L bond on the nature of the porphyrin and the basicity of the additional molecular ligand was determined from the experimental data and calculation results.

Spectral–Luminescence Properties of Molecular Complexes of Photoconductive Polymers with Neutral Organic Acceptors

It has been found that in films of aryl– and alkyl–substituted polysilanes -- poly(methylphenylsilane) and poly(dihexylsilanes) -- the molecules of electron acceptors of tetracyanoquinodimethane, dinitrofluorenone, and trinitrofluorenone form weak complexes with charge transfer from the longest segments of the polymeric chain. The absorption and luminescence spectra of these complexes are similar to the spectra of complexes formed by the carbonyl groups of poly–N–epoxypropyl carbazole with the above acceptors and consist of wide bands situated in the visible range of wavelengths.

Structure of luminescence spectra for molecular anions CrO 4 2− , adsorbed on the surface of dispersed silicon dioxide

The tetrahedral molecular anion CrO~-, when introduced in matrices of various compositions and structures, serves as a convenient system for the study of electronic--vibrational, vibrational-vibrational, and spin--orbit interactions in molecular impurity centers [i]. At low temperatures, such impure crystals exhibit an intense luminescence which provides a way to carry out a number of studies of absorption and emission centers. Thus, it has been shown the CrO~forms complexes with anionic vacancies and with Me + cations (Na +, K +, Rb +, etc.), and also with Me 2+ dopant cations (Ca 2+, Sr 2+, Ba2+), forming centers of several types with different local symmetry at the molecular anion. The luminescence properties of molecular complexes involving CrO~depend on the composition of the complex and on its structure, as well as on the local symmetry of the molecular anion in the complex. It has also been shown [i, 2] that the smallest value of the electron-phonon interaction (where the crystals exhibit clear vibronic structure in the absorption, luminescence, and excitation spectra) and the highest quantum yield are characteristic of complexes with the highest possible local symmetry for a tetrahedral molecular anion, namely C3v.

CNDO/2 Study on molecular complexes of aliphatic amines with HF and F2

Abstract Properties of molecular complexes formed between aliphatic amines with HF and F2, respectively, have been evaluated by the CNDO/2 method. In the amineHF hydrogen-bonded complexes the calculated properties (binding energy, amount of charge transferred, enhancement of dipole moment) are fairly constant in the series of systems studied. In the amineF2 charge transfer complexes the binding energy decreases and the amount of charge transferred slightly increases with the lowering of the amine's ionization potential. The results obtained are discussed in relation to the electronic structure of the complexes formed.

Solvent-Inclusion Effects on the Structures and Properties of Molecular Complexes and Radical Salts

Abstract Some molecular complexes and radical salts give the crystal forms which contain solvent molecules in their crystal lattices, and these solvated crystals often exhibit physical properties markedly different from those of the solventfree crystals. Two typical examples of such cases, on which we have recently investigated, will be described here to illustrate the characteristic features of solvent-inclusion.

Structures and properties of molecular complexes of iodine with azoles

Structures and properties of molecular complexes of iodine with azoles

Formation and Properties of Molecular Complexes in the Excited State

Formation and Properties of Molecular Complexes in the Excited State