TY - JOUR
T1 - Twisted π-electron system electrooptic chromophores. Structural and electronic consequences of relaxing twist-inducing nonbonded repulsions
AU - Wang, Yiliang
AU - Frattarelli, David L.
AU - Facchetti, Antonio
AU - Cariati, Elena
AU - Tordin, Elisa
AU - Ugo, Renato
AU - Zuccaccia, Cristiano
AU - Macchioni, Alceo
AU - Wegener, Staci L.
AU - Stern, Charlotte L.
AU - Ratner, Mark A.
AU - Marks, Tobin J.
PY - 2008/5/29
Y1 - 2008/5/29
N2 - The synthesis, structural and spectroscopic characterization, and nonlinear optical response properties of a "slightly" twisted zwitterionic 4-quinopyran electrooptic chromophore FMC, 2-{4-[1-(2-propylheptyl)-1H-pyridine- 4-ylidene]cyclohexa-2,5-dienylidene}malononitrile, are reported. X-ray diffraction data and density functional theory (DFT) minimized geometries confirm that deletion of the four o-, o′-, o″-, and o‴-methyl groups in the parent chromophore TMC-2, 2-{4-[3,5-dimethyl-1-(2-propylheptyl)- 1H-pyridin-4-ylidene]-3,5-dimethylcyclohexa-2,5-dienylidene}malononitrile, relaxes the arene-arene twist angle from 89.6 to 9.0°. These geometrical changes result in a significantly increased contribution of the quinoidal structure to the molecular ground state of FMC (versus TMC-2), reduced solvatochromic shifts in the optical spectra, and a diminished electric-field-induced second-harmonic (EFISH) generation derived molecular hyperpolarizability (μβ = -2340 × 10-48 esu of DFMC, the dendrimer derivative of FMC, vs -24000 × 10-48 esu of TMC-2) in CH2Cl2 at 1907 nm. Pulsed field gradient spin-echo (PGSE) NMR spectroscopy and EFISH indicate that the levels of FMC aggregation in solution are comparable to those of TMC-2 (monomers and dimers) in CH2Cl2 solution. B3LYP and INDO/S computation of chromophore molecular structure, aggregation, and hyperpolarizability trends are in good agreement with experiment.
AB - The synthesis, structural and spectroscopic characterization, and nonlinear optical response properties of a "slightly" twisted zwitterionic 4-quinopyran electrooptic chromophore FMC, 2-{4-[1-(2-propylheptyl)-1H-pyridine- 4-ylidene]cyclohexa-2,5-dienylidene}malononitrile, are reported. X-ray diffraction data and density functional theory (DFT) minimized geometries confirm that deletion of the four o-, o′-, o″-, and o‴-methyl groups in the parent chromophore TMC-2, 2-{4-[3,5-dimethyl-1-(2-propylheptyl)- 1H-pyridin-4-ylidene]-3,5-dimethylcyclohexa-2,5-dienylidene}malononitrile, relaxes the arene-arene twist angle from 89.6 to 9.0°. These geometrical changes result in a significantly increased contribution of the quinoidal structure to the molecular ground state of FMC (versus TMC-2), reduced solvatochromic shifts in the optical spectra, and a diminished electric-field-induced second-harmonic (EFISH) generation derived molecular hyperpolarizability (μβ = -2340 × 10-48 esu of DFMC, the dendrimer derivative of FMC, vs -24000 × 10-48 esu of TMC-2) in CH2Cl2 at 1907 nm. Pulsed field gradient spin-echo (PGSE) NMR spectroscopy and EFISH indicate that the levels of FMC aggregation in solution are comparable to those of TMC-2 (monomers and dimers) in CH2Cl2 solution. B3LYP and INDO/S computation of chromophore molecular structure, aggregation, and hyperpolarizability trends are in good agreement with experiment.
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U2 - 10.1021/jp8003135
DO - 10.1021/jp8003135
M3 - Article
AN - SCOPUS:53449085539
VL - 112
SP - 8005
EP - 8015
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 21
ER -