Title

Carbazole Based Ambipolar Compounds: A Study of Their Intramolecular Charge Transfer Properties

Date of Award

2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Douglas Neckers, PhD

Second Advisor

Massimo Olivucci, PhD (Committee Co-Chair)

Third Advisor

Marshall Wilson, PhD (Committee Member)

Fourth Advisor

Felix Castellano, PhD (Committee Member)

Fifth Advisor

Lee Meserve, PhD

Abstract

The present manuscript describes the synthesis and photophysical properties of six carbazole-based ambipolar compounds with donor-acceptor-donor (hereafter D-A-D) configuration in C2v symmetric arrangement. Three acceptor units were chosen based on their known optical properties, symmetry and planarity: fluorenone (FO), fluoren-9-ylidene malononitrile (FM), and dibenz[a,c]phenazine (Pz). Such units were connected through a phenylacetylene (PA) bridge (B) to favor structural rigidity and keep D-A distances fairly constant. The acceptor unit was functionalized through their common biphenylene skeleton via 3,3' and 4,4' substitutions (in the manuscript they adopt the numerology from fluorene). The triads B-A-B were also synthesized for comparison purposes. The photophysical properties have been investigated by means of steady state and time resolved UV-Vis absorption and photoluminescence, plus cyclic voltammetry. Computational methods such as density functional theory (DFT) and post self-consistent field (SCF) (i.e. complete active space SCF, or CASSCF) were utilized to map the electronic properties of the derivatives and perform a first survey of the possible non-radiative relaxation mechanism of their S1 state. The focus of these studies was based on the structure-activity relationship between the pattern of substitution and the electronic properties of the bulk. This helped establishing design patterns for the next generation of chromophores to be utilized in organic electronics applications such as thin-film transistors and photovoltaics, based on these D and A units.