Third-order NLO property of beryllium-pyridyne complexes

Six pyridyne isomers and their complexes with beryllium have been considered for the theoretical study of the third-order polarizability. The NLO properties are calculated by employing the DFT functionals BLYP, B3LYP, BHHLYP, B3PW91, BP86 and B2PLYP for the 6-311++G(d,p) basis set. The C - Be bond length in the complexes varies within 1.644 Å–1.771 Å indicating covalent interactions between the metal and pyridynes. The present investigation reveals that the magnitude of second-hyperpolarizability of pyridynes strongly enhances upon complex formation with beryllium. The maximum hyperpolarizability has been predicted for the 2,5-diberyllium pyridine complex. The lowest value of hyperpolarizability is obtained for the 2,3- and 3,4-diberyllium pyridine complexes. The chosen DFT methods predict almost identical pattern of variation of NLO property. The variation of second-hyperpolarizability has been satisfactorily explained by the excitation energy and transition dipole moment associated with the most dominant excited state.

MOLECULAR STRUCTURE, NATURAL BOND ORBITAL, SUBSTITUENT EFFECT AND CHEMICAL REACTIVITY ANALYSIS OF TERMINAL BORYLENE RUTHENIUM COMPLEXES: Ru(PH3)2HCl(BC6H4X)

The structure and properties of a terminal borylene ruthenium complexes Ru ( PH 3)2 HCl ( BC 6 H 4X) have been investigated using theoretical methods. Frontier orbital analysis indicates the HOMO is distributed on the Ru and Cl ligand. On the other hand, LUMO is distributed on the Ru and phenyl ligand. The influence of solvent on the structure and properties of X = H structure has been studied. Time-dependent density functional theory (TD-DFT) is used to calculate the energy, oscillatory strength and wavelength absorption maxima (λmax) of various electronic transitions and their nature within molecules. Nonlinear optical (NLO) behavior of title compounds is investigated by the computed value of first hyperpolarizability (βtotal).

DFT STUDY OF SOME TRIVALENT d- AND f-BLOCK METAL ION COMPLEXES OF ALLOXAN

Density functional calculations have been employed to elucidate the structures of some six coordinated complexes of alloxan monohydrate with some d- and f-block metals. Alloxan monohydrate may exist in the mono-ionized or di-ionized form in its complexes, and both states were investigated. It is found that when the metal ion is coordinated to three bidentate ligands, the structures are nearly trigonal prismatic, but replacement of a bidendate ligand by two monovalent ligands changes the geometry to deformed octahedral. The metal-alloxanate bonding is largely ionic for the lanthanoids. The calculated vibrational frequencies are in agreement with the experimentally determined ones.

THEORETICAL INVESTIGATION ON PHOTOISOMERIZATION SWITCHABLE SECOND-ORDER NONLINEAR OPTICAL PROPERTIES OF Λ-SHAPED DIARYLETHENE DERIVATIVES

The nonlinear optical (NLO) properties of Λ-shaped diarylethene (DAE) derivatives 1a(b)–4a(b) and their NLO switching effects were studied by using the density functional theory (DFT) methods. The results demonstrate that all of the open-ring molecules and their own closed-ring forms meet the model of NLO switching tuned by photoisomerization. The βtot values of 1b–3b are 16 times as small as that of their open-ring forms, and βtot value of 4b is 4 times as large as that of 4a. The spin interactions of open-shell closed-ring molecules are larger than that of their open-ring forms, and it could increase the NLO responses to some degree. Nature bond orbital (NBO) calculations indicate that large charge differences between electron-deficient and electron-rich centers are beneficial to charge transfer (CT), and the overlap between frontier molecular orbital (FMO) is also advantageous to the CT and NLO responses. Time-dependent density functional theory (TD-DFT) calculations show βtot values of all molecules meet the two-level model very well, and the smaller the ΔE ge , the larger the βtot value.

ACHIEVING P-TYPE SEMICONDUCTING ZnO NANOWIRES VIA DONOR ADSORPTION

The difficulty of achieving p-type conductance has severely limited the application of ZnO to electronic devices. In this work, we propose a simple and effective way to achieving p-type semiconducting ZnO nanowires (NWs) through density functional theory computations. Adsorption of tetrathiafulvalene (TTF) during synthetic procedures leads to lower formation energies, and accordingly higher concentration of p-type defects; after the formation of ZnO NWs and the desorption of TTF, p-type ZnO NWs can be achieved. Also, we present a facile synthesis route on basis of previous experiments, which provides some guidance for the realization of p-type ZnO NWs.