Ab initio RHF calculations have been used to study the relative variation of βe and βv in D/A (NH2/NO2) substituted π-conjugated compounds as a function of the specific nature, length, and charge of the linker. For the vibrational property we have separated off the contribution due low-frequency (ω≤100 cm-1) modes, which have long response times and are associated primarily with torsional motions. For all cases considered the βv; 100(0)/βe(0) ratio lies in the range 1.35-6.58. In our systematic comparisons we have found that increases in βe are most often accompanied by increases in βv. Similar behavior has also been obtained previously for a series of mono- and di-substituted benzenes. However, there are counter-examples as well: when the conjugation is broken by inserting an sp3 defect, when changing the nature of the aromatic rings in stilbene-like linkers and, more importantly, upon doping α,ω-nitro,amino all-trans polyene chains.
|Number of pages||14|
|Journal||Chemical Physics Letters|
|Publication status||Published - 1 Jul 1999|