Design, synthesis, spectroscopy, and Hammett correlation analysis of heteroarylethynyl donor-acceptor porphyrin systems for electro-optic applications

This thesis focuses on the rational design, synthesis, spectroscopic characterization, photophysics, and structure-property correlation analysis of a host of novel nonlinear optical (NLO) donor-acceptor (hetero)arylethynyl porphyrin chromophores. These compounds have been designed both as NLO monomeric chromophores for incorporation into functional electrooptic polymers and as an integrated family for elucidation of structure-property relationships.; One of the key accomplishments in this work has been the rational design and synthesis of a host of donor-π-bridge-acceptor systems featuring a myriad of donor, acceptor, and bridging moieties. Another key accomplishment in this work has been the first synthesis of a trans meso 4-dimethylaminophenylethynyl elaborated, electron-rich Suzuki porphyrin synthon, which enabled the synthesis of highly functionalized asymmetric donor-acceptor porphyrin structures not accessible via conventional synthetic routes. Another important aspect of this thesis involved the derivatization of the prototype push-pull arylethynyl porphyrin into polymer-ready hydroxy and amino functionalized versions for incorporation and organization into processable polymeric matrices.; Three interrelated classes of compounds were featured: (i) The polymer-ready donor-functionalized NLO porphyrins featuring mono(hydroxyalkyl), bis(hydroxyalkyl), mono(aminoalkyl), and bis(aminophenyl) functionalities; (ii) The novel series of (hetero)arylethynyl push-pull porphyrins featuring such donor moieties as N-phenyl and N-thienyl triphenylamines, N-phenyl and N-thienyl carbazoles, and 3-ethylcarbazol-3-yl, and such potent acceptors as 5-nitrothiazole, 6-nitrobenzothiazole, and terminally nitro substituted oligothiophenes; and (iii) A family of novel meso oligothiophene-substituted asymmetric porphyrins featuring both 5-(4-dimethylaminophenylethynyl) donor and trans meso directly linked 5-nitro oligothiophene acceptors.; A newly-coined Hammett parameter, reduced Hammett constant, has been proposed and defined in rationalizing successfully the relationship between the chromophore photophysics and the potency of donor/acceptor moieties involving different (hetero)aromatic bridges. This newly defined parameter facilitates quantitative comparison of the efficacy of different π bridges in the transmission of substituent effect.; Both photophysics and Hammett correlation analysis predicted that some of the chromophores are expected to possess augmented second-order NLO properties compared to the prototype chromophore which have exhibited outstanding μβ values. The molecular first-order hyperpolarizabilities of these chromophores are being evaluated with hyper-Rayleigh scattering techniques.