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Photochromic Isomerization of a Dinuclear Molybdenum Complex with Ethylene-1,2-Dithiolate and Disulfur Ligands:  X-ray Structures of the Two Isomers

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journal contribution
posted on 23.01.2003, 00:00 by Takashi Shibahara, Masanobu Tsuboi, Shinsuke Nakaoka, Yasuhiro Ide
A photochromic complex with disulfur and dimethyl-ethylene-1,2-dithiolate ligands, [Mo2(μ-S2)(μ-S2C2Me2)2(S2C2Me2)2] (3), was synthesized and characterized. Photoirradiation of 3 with visible light resulted in the formation of the isomer (3‘). The electronic spectrum of 3‘ has a new intense peak in the near infrared region, and in the dark, the spectrum returns to that of 3. X-ray structural analyses of 3·C6H6 and 3‘ revealed a large conformational change of the bridging dithiolate ligands:  the two ligands in 3‘ come very close to each other compared to those in 3·C6H6. Crystal data:  3·C6H6, monoclinic, space group C2/c, a = 15.193(4) Å, b = 14.287(3) Å, c = 14.685(4) Å, β = 105.30(1)°, V = 3074(1) Å3, Z = 4; 3‘, monoclinic, space group C2/c, a = 21.5400(8) Å, b = 9.5232(5) Å, c = 13.9828(2) Å, β = 118.924(1)°, V = 2510.5(2) Å3, Z = 4. 1H NMR spectra of 3 (3.06, 3.05, 1.66, and 1.31 ppm) and 3‘ (2.90, 2.75, 2.14, and 1.97 ppm) are also reported:  each spectrum has four signals due to methyl groups, which accords well with the fact that each of the molecules, 3·C6H6 and 3‘, has a crystallographic 2-fold axis.