Synthesis and Structural Studies of Donor-Bridge-Acceptor Complexes Based on Co(III) (CYCLAM) Acetylides
Abstract
Obtaining a greater understanding of photo-induced electron-transfer (PET) processes is key to synthesizing photovoltaic materials with enhanced efficiency. Gaining knowledge about the structure property relationship in photo-active donor-bridge-acceptor (D-B-A) dyads will help to optimize electronic and photoelectronic materials. Metal acetylide complexes have attracted increasing interest for their potential applications as building blocks for electronic and photoelectronic materials. Their unique υ(C≡C) (2000-2100 cm-1 ) allows for selective excitation, making them an appealing target for attenuating PET processes across a metal acetylide backbone. The following topics will be discussed: i.) an overview of M(cyclam′) alkynyl chemistry, where M = Cr, Fe, Co, or Ni, with a focus on reactivity and spectroscopy, ii.) selective synthesis of dissymmetric species, utilizing a CoIII(cyclam) (1,4,8,11-tetraazacyclotetradecane) alkynyl bridge, iii) synthesis and characterization of metal alkynyl D-B-A dyads trans- [R'2N-4-C6H4C2-CoIII(cyclam)-Cn-NAPR ] + (n = 2 or 4), where the chromophore acceptor is NAPiPr (N-isopropyl-1,8-napthalimide) and the putative donor is -C6H4-4-NR'2 (R' = Me or Ph-4-OMe), iv.) design and synthesis of D-B-A derivatives, alter NAPR (R = mesityl, methyl, 1-ethylpropyl, 2-ethylhexyl, or octyl) to tune reactivity and crystallinity, v.) electronic and spectroscopic influence the bridging center on A, and vi.) effect of η2 coordination of MX2 (MX2 = CuCl2 or Ag(NO3)2) to the alkyne bridge on electron transfer. Both the B-A and D-B-A type compounds have been structurally characterized through single crystal X-ray diffraction, and spectroscopically characterized through UVvis, FTIR, and fluorescence spectroscopy. It is concluded based on both the voltammetric and spectroscopic analysis of D-B-A that (i) the HOMO and LUMO are localized on donor and acceptor respectively; (ii) the π-π* transition localized on NAPR (ca. 390 nm) is the primary Franck-Condon excitation; and (iii) the emissions of both the B-A and D-BA moieties are fluorescent in nature and dominated by NAPR when R' = Me. Through collaborations, we are currently probing the evolution of initial excited state(s) in D-B-Aand its vibronic attenuation using ultra-fast timescale pump(UV)-probe(IR) and pump(UV)-pump(IR)-probe(IR) techniques, respectively.
Degree
Ph.D.
Advisors
Ren, Purdue University.
Subject Area
Alternative Energy|Materials science|Electromagnetics
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