NOVEL CHIRAL BIS-DIPOLAR 6,6'-DISUBSTITUTED BINAPHTHOL DERIVATIVES FOR 2ND-ORDER NONLINEAR OPTICS - SYNTHESIS AND LINEAR AND NONLINEAR-OPTICAL PROPERTIES

A number of thermally and optically stable, bis-dipolar chiral molecul es based on two geometries of the binaphthol (BN) system with differen t acceptors/substituents have been synthesized for the first time, and the synthetic routes are reported: optically pure 6,6'-disubstituted 2,2'-diethoxy-1,1'-binaphthyls {R, R'= -Br, -CHO, -CH=C(CN)(COOEt), -C H=C(CN)(2), -CH=CHCN, -CH=CH(p-NO(2)Ph)} and optically pure 9,14-disub stituted dinaphtho[2,1-d: 1',2'-f][1,3]dioxepins {R, R' = -Br, -CHO, - CH=C(CN)(COOEt), -CH=C(CN)(2), -CH=CHCN, -CH=CHSO2CH3, -CH=CHCHO, -CH= CHCH=C(CN)(2)}. All molecules possess two equal donor--acceptor system s linked together to give a bis-dipolar system. Two mono-dipolar 6-sub stituted 2-butoxynaphthalene (R = -CH=C(CN)(2), -CH=C(CN)(COOEt)) dono r--acceptor systems were prepared as references. The linear optical pr operties including solvatochromic shifts of absorption and fluorescenc e revealed strong charge transfer excitations in the new dipolar syste ms. The molecules show a high first hyperpolarizability beta (up to (3 44-364) x 10(-30) esu) as measured by electric-field-induced second-ha rmonic generation (EFISHG) and hyper-Rayleigh scattering (HRS). A mode l is developed to express the first hyperpolarizability of the bis-dip olar molecules in terms of the molecular geometry and the beta of the monomeric donor-acceptor units. The tensor components were determined experimentally using this model and data from HRS and EFISHG. These te chniques probe different combinations of the components of the molecul ar hyperpolarizability tenser. The results obtained are found to be in excellent mutual agreement.