TY - JOUR
T1 - Ultra-High-Response, Multiply Twisted Electro-optic Chromophores
T2 - Influence of π-System Elongation and Interplanar Torsion on Hyperpolarizability
AU - Shi, Yanrong
AU - Frattarelli, David
AU - Watanabe, Naoki
AU - Facchetti, Antonio
AU - Cariati, Elena
AU - Righetto, Stefania
AU - Tordin, Elisa
AU - Zuccaccia, Cristiano
AU - Macchioni, Alceo
AU - Wegener, Staci L.
AU - Stern, Charlotte L.
AU - Ratner, Mark A
AU - Marks, Tobin Jay
PY - 2015/10/7
Y1 - 2015/10/7
N2 - The systematic synthesis, structural, optical spectroscopic, and second-order nonlinear optical (NLO) characterization of a series of donor-acceptor poly-arylene chromophores which have heretofore unachieved π-extension and substantial twisting from planarity, are reported: specifically, two-ring 2TTMC, dicyano(4-(3,5-dimethyl-1-(2-propylheptyl)pyridin-1-ium-4-yl)-3-methylphenyl)methanide; three-ring 3TTMC, dicyano(4′-(3,5-dimethyl-1-(2-propylheptyl)pyridin-1-ium-4-yl)-2,2′,3′,5′,6′-pentamethyl[1,1′-biphenyl]-4-yl)methanide; and four-ring 4TTMC, dicyano(4-(3,5-dimethyl-1-(2-propylheptyl)pyridin-1-ium-4-yl)-2,2′,3,6,6′-pentamethyl[1,1′:4′,1-terphenyl]-4-yl)methanide. Single-crystal X-ray diffraction, DFT-optimized geometries, and B3LYP/INDO-SOS analysis identify three key features underlying the very large NLO response: (1) For ring catenation of three or greater, sterically enforced π-system twists are only essential near the chromophore donor and acceptor sites to ensure large NLO responses. (2) For synthetic efficiency, deletion of one ortho-methyl group from o,o′,o,o-tetramethylbiaryl junctures, only slightly relaxes the biaryl twist angle from 89.6° to 80°. (3) Increased arylene catenation from two to three to four rings (2TTMC,3TTMC,4TTMC) greatly enhances NLO response, zwitterionic charge localization, and thus the ground-state dipole moment, consistent with the contracted antiparallel solid-state π-π stacking distances of 8.665,7.883,7.361 Å, respectively. This supports zwitterionic ground states in these chromophores as do significant optical spectroscopic solvatochromic shifts, with aryl-aryl twisting turning on significant intra-subfragment absorption. Computed molecular hyperpolarizabilities (μβ) approach an unprecedented 900 000 × 10-48 esu, while estimated chromophore figures of merit, μβvec/Mw, approach 1500 × 10-48 esu, 1.5 times larger than the highest known values for twisted chromophores and >33 times larger than that of planar donor-acceptor chromophores.
AB - The systematic synthesis, structural, optical spectroscopic, and second-order nonlinear optical (NLO) characterization of a series of donor-acceptor poly-arylene chromophores which have heretofore unachieved π-extension and substantial twisting from planarity, are reported: specifically, two-ring 2TTMC, dicyano(4-(3,5-dimethyl-1-(2-propylheptyl)pyridin-1-ium-4-yl)-3-methylphenyl)methanide; three-ring 3TTMC, dicyano(4′-(3,5-dimethyl-1-(2-propylheptyl)pyridin-1-ium-4-yl)-2,2′,3′,5′,6′-pentamethyl[1,1′-biphenyl]-4-yl)methanide; and four-ring 4TTMC, dicyano(4-(3,5-dimethyl-1-(2-propylheptyl)pyridin-1-ium-4-yl)-2,2′,3,6,6′-pentamethyl[1,1′:4′,1-terphenyl]-4-yl)methanide. Single-crystal X-ray diffraction, DFT-optimized geometries, and B3LYP/INDO-SOS analysis identify three key features underlying the very large NLO response: (1) For ring catenation of three or greater, sterically enforced π-system twists are only essential near the chromophore donor and acceptor sites to ensure large NLO responses. (2) For synthetic efficiency, deletion of one ortho-methyl group from o,o′,o,o-tetramethylbiaryl junctures, only slightly relaxes the biaryl twist angle from 89.6° to 80°. (3) Increased arylene catenation from two to three to four rings (2TTMC,3TTMC,4TTMC) greatly enhances NLO response, zwitterionic charge localization, and thus the ground-state dipole moment, consistent with the contracted antiparallel solid-state π-π stacking distances of 8.665,7.883,7.361 Å, respectively. This supports zwitterionic ground states in these chromophores as do significant optical spectroscopic solvatochromic shifts, with aryl-aryl twisting turning on significant intra-subfragment absorption. Computed molecular hyperpolarizabilities (μβ) approach an unprecedented 900 000 × 10-48 esu, while estimated chromophore figures of merit, μβvec/Mw, approach 1500 × 10-48 esu, 1.5 times larger than the highest known values for twisted chromophores and >33 times larger than that of planar donor-acceptor chromophores.
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U2 - 10.1021/jacs.5b04636
DO - 10.1021/jacs.5b04636
M3 - Article
C2 - 26360110
AN - SCOPUS:84943552342
VL - 137
SP - 12521
EP - 12538
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 39
ER -