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Exciton coupling effects and conformational change of perhexyloligosilanes with optically active methyl(1‐naphthyl)phenylsilyl terminals
Author(s) -
Oh HyunShik,
Park LeeSoon,
Kawakami Yusuke
Publication year - 2003
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.10276
Subject(s) - bathochromic shift , chromophore , chemistry , exciton , chirality (physics) , crystallography , conjugated system , stereochemistry , lambda , absorption (acoustics) , wavelength , photochemistry , fluorescence , polymer , physics , optics , organic chemistry , chiral symmetry breaking , quantum mechanics , nambu–jona lasinio model , quark
Perhexyloligosilanes ( R,R )‐(+)‐MeNpPhSi*(Hex 2 Si) n Si*PhNpMe (n = 2; ( R,R )‐(+)‐ 4a, n = 4; ( R,R )‐(+)‐ 6a, n = 6; ( R,R )‐(+)‐ 8a ) with chiral methyl(1‐naphthyl)phenylsilyl terminals were synthesized and characterized. The absorption wavelengths λ max by 1 L a,Ph transition of phenyl chromophore conjugated with oligosilane units in ( R,R )‐(+)‐ 4a – ( R,R )‐(+)‐ 8a show bathochromic shift of about 3–4 nm compared with those of the α,ω‐phenyl substituted perhexyloligosilanes Ph(Hex 2 Si) m Ph (m = 4; 4b, m = 6; 6b, m = 8; 8b ) having the same silicon chain length. Longer chain length induces the separated λ max of 1 L a,Ph from 1 B b,Np of naphthyl chromophore with positive exciton chiralities. In ( R,R )‐(+)‐ 8a, although the extremum wavelengths λ ext of exciton coupling between 1 B b,Np and 1 L a,Ph are separated by about 80 nm, the compound retains the positive exciton chirality, which provides definite information on the absolute configuration of terminal chiral silicon atoms. Bulky terminal substituents and lowering the temperature affect the conformation of the main chain, inducing extended silicon backbone structure. Chirality 15:646–653, 2003. © 2003 Wiley‐Liss, Inc.