تصميم ودراسة مواد هجينة جديدة ككرموفورات ضوئية لا خطية

Design and Investigation of New Hybrid Materials as Nonlinear Optical Chromophores

Abstract
Three sections make up this thesis. An introduction to non-linear optical (NLO) materials and second-harmonic Generation (SHG) formation is covered in the first section, along with an explanation of the donor-acceptor relationship and how bridges are used in the Two-State Model to connect them. Additionally Polyoxometalate (POM)and its variants, are discussed as well as pyrene, the strongest doner known. The second section examines the Schrödinger equation, includes four key approximations, quantum chemistry, and Hartree-Fock (HF). It also TDDFT, DFT, and other related subjects. All of the results were described in the third part. Through second-order phenomena like second harmonic production (frequency doubling) and third-order effects like multi-photon absorption, non-linear optical (NLO) materials are utilized to alter laser light. This thesis focuses on NLO materials that include phenyl-imido groups that link organic electron donors to polyoxometalate (POM) electron acceptors. We have thoroughly investigated novel compounds as strong NLO chemicals, such as pyrene-based donor groups, which are incredibly powerful donors, both theoretically and mostly by DFT calculations. Additionally, their linear optical properties, second-order nonlinear responses, and geometric and electrical structures have all been assessed. Moreover, the effects of substitutions (such alkyl and phenyl groups) on the donor strength of pyrene and, therefore, on the responses have been investigated. Anion 5 produced a remarkable NLO responses of up to (1349 ×10-30esu) an increase of ≈ 2 compared to its un-methylated analogue (anion 2).TD-DFT calculations indicate that the strong low-energy transition is mainly caused by the charge transfer (CT) from pyrene arylamide to the hexamolybdate cluster. According to this, the compounds’ linear and non-linear optical behaviour is caused by substantial communication between the POM and pyrene components. Even though it drastically lessens the initial hyperpolarizability, ortho-methylation of the imido-bond has a considerable impact on the stability and, consequently, the length and linearity of the bond as well as the NLO activity. While maintaining a respectably high transparency wind, the TDDFT results show that the pyrene-POMs combination exhibits extraordinary NLO activity in comparison to similar simply organic systems.