Chiroptical properties of diaryl-spiro-lambda(4)-sulfanes: An exciton chirality model

An exciton couplet was found in the L-1(a) region of the CD spectrum of opt ically active 1,1'-spirobi[H-3-2,1-benzoxathiol]-3-one with known absolute configuration {(R)-(+)-2}. Other spiro-lambda(4)-sulfanes containing two be nzene rings (1a-b, 3a-b) showed similar spectra. No couplet-like bands were seen in the CD spectrum of the naphthalene derivative 5, but the interacti on between the benzene L-1(a) and the naphthalene B-1(b) transitions in the molecule 6 also caused splitting due to exciton coupling. CD spectroscopy allows a determination of the absolute configuration of trigonal bipyramida l spiro-lambda(4)-sulfanes 1-3 by using the exciton chirality method.