The effect of different bithienyl spacers on the linear and non-linear optical properties of organometallic chromophores derived from [Fe-2(eta(5)-C5H5)(2)(CO)(2)(mu-C-CH3)](+) [BF4](-) crystal structure of [Fe-2(eta(5)-C5H5)(2)(CO)(2)(mu-CO)(mu-(E)-C-CH=CH-7-(thieno[3,2-e][1]benzothiophene))](+) [BF4](-)

Two series of organometallic merocyanines incorporating a variety of bithie nyl moieties both as spacers and end groups were synthesised, In the first series the bithienyls function as end groups and were appended to an accept or derived from [Fe-2(eta (5)-C5H5)(2)(CO)(2)(mu -CO)(mu -C-CH3)](+) [BF4]( -). In the second series, ferrocene acting as an organometallic donor was i ncorporated into the chromophores at the far terminus of the bithienyl spac ers. The molecular first hyperpolarisabilities beta of the second series we re determined by hyper-Rayleigh scattering and the values range from 429 x 10(-30) esu to 867 x 10-30 esu in dichloromethane. A single crystal X-ray s tudy of [Fe-2(eta (5)-C5H5)(2)(CO)(2)(mu -CO)(2)(mu-(E)-C-CH=CH-7-(thieno[3 ,2-e][1]benzothiophene))](+) [BF4](-). CH2Cl2 is reported. (C) 2001 Elsevie r Science B.V. All rights reserved.