Computational Study of Structural and Optical Properties of Metal Alkynyl Complexes

Abstract

The interaction of light with a nonlinear optical (NLO) material gives rise to new optical fields with altered properties (e.g. phase, frequency, amplitude, polarization, path, etc.), which are of utmost importance for photonic applications. The search for new efficient NLO materials for applications has thus been accelerated. In particular, interest in the NLO properties of organometallic systems has undergone enormous growth in the past decade. This thesis consists of a compilation of several papers relating to the experimental and density functional theory (DFT) studies of the nonlinear optical properties of metal alkynyl complexes. Paper 1 includes a brief introduction to nonlinear optical phenomena, in particular to the second-order NLO effects, and the popular experimental and quantum chemical methods for the determination of molecular first hyperpolarizability. It also includes a comprehensive review of previous semi empirical and DFT NLO calculations relating to organometallic complexes. Paper 2 deals with the benchmarking of DFT methods for first hyperpolarizabilities and excitation energies of metal alkynyls against the relevant experimental data. Papers 3-9 are combined experimental and computational (DFT) studies of dipolar (paper 3-8) and octupolar (paper 9) metal alkynyl complexes. The contribution from the calculations to each paper is as follows. In paper 3, linear optical and quadratic nonlinear optical properties of alkynyl complexes with different ligated metal centres (Ru, Ni, and Au) and with different bridges (phenylene, naphthalenylene, and anthracenylene) are calculated with DFT and time dependent DFT (TD-DFT). In paper 4, the linear optical and quadratic nonlinear optical properties of ruthenium alkynyl complexes with oligo(phenylenevinylene) bridges were calculated using DFT and the results compared with the experimental data. In paper 5, the experimentally determined linear optical properties and first hyperpolarizabilities of some ruthenium alkynyl complexes with yne/ene/azo inter-ring linkers are rationalized by DFT/TD-DFT calculations. In paper 6, the structural, linear optical, and nonlinear optical properties of ruthenium alkynyl complexes with P–P (= dppf, dppb, and dppe) and N–N (4,4’-di-tert-butyl-2,2’-bipyridine) donor co-ligands were rationalized from DFT calculations. Paper 7 consists of TD-DFT calculations undertaken on a series of bis(alkynyl) Ru complexes to rationalize the experimental linear optical data. In paper 8, the mechanism of two-dimensional NLO character in Y-shaped ruthenium alkynyl complexes is studied with the use of DFT/TD-DFT calculations. In paper 9, computational studies were undertaken to assign the key optical transitions for some octupolar compounds bearing (N-heterocyclic carbene) gold or diphenylamino substituents at the periphery. Show more