Effects of TIPS-Functionalization and Perhalogenation on the Electronic, Optical, and Transport Properties of Angular and Compact Dibenzochrysene

We report a systematic comparative
study on dibenzo­[b,def]­chrysene
(angular) and dibenzo­[def,mno] chrysene (compact) polyaromatic hydrocarbons
and their bis-tri­isopropyl­silyl­ethynyl (TIPS)-functionalized
and perhalogenated (F, Cl) counterparts. We used density functional
theory (DFT) and time-dependent DFT to quantify the effects of morphology
and chemical modifications on the electronic, optical, and transport
properties. In particular, we compared electron affinity, ionization
energy, fundamental gap, optical absorption, exciton binding energy,
and reorganization energies for holes and electrons. For both TIPS-functionalization
and halogen substitutions, we found larger electron affinities (nearly
tripled with perchlorination). Ionization energies are found to be
reduced for TIPS-functionalization (by ∼5%) and enhanced following
halogen substitution (up to 17%). In both compact and angular dibenzochrysenes,
the above trends reflect in a general reduction of the fundamental
gap (up to 22%) following chemical modification. The effect
of perhalogenation and TIPS-functionalization is always to increase
molecular reorganization energies for both holes and electrons. Concerning the optical properties, we observe a redshift of the
optical onset in all cases; for TIPS-functionalized molecules, in
particular, we additionally found a remarkable enhancement of the
absorption in the visible region.