The vibrational, optical, and nonlinear optical (NLO) properties of a series of push-pull chro
mophores builtaround dithienylethylene-based
mages/gifchars/pi.gif" BORDER=0 >-conjugating spacers have been investigated by UV-vis, IR, and Ra
manspectroscopies and electric field-induced second har
monic generation (EFISH)
measure
ments. The effects ofthe strength of the acceptor group on the
molecular electronic properties of these conjugated NLO chro
mophoreshave been addressed. The
magnitude of the intra
molecular charge transfer has been tested as a function ofthe acceptor strength and of the bridging of the spacer. Density functional theory (DFT) calculations havebeen perfor
med to help the assign
ment of the
main electronic and vibrational features of the NLO chro
mophoresand to derive useful infor
mation about their
molecular structures. EFISH
measure
ments show that push-pullsyste
ms that contain strong electron-acceptor groups connected via a rigidified dithienylene spacer exhibitlarge values of
mages/entities/
mgr.gif">
mages/gifchars/beta2.gif" BORDER=0 ALIGN="
middle">
0. Theoretical NLO calculations are in excellent agree
ment with experi
mental results. Thegeo
metrical and electronic properties calculated in solution reveal that chro
mophores beco
me highly polarizedas the dielectric constant of the solvent increases. The spectroscopic properties/structure relationships agreewith the observation that
mages/gifchars/beta2.gif" BORDER=0 ALIGN="
middle">
0 increases upon the covalent bridging of the spacer and with the increase of theacceptor strength.