Structures and Non-linear Optical Properties of Multi-Sulfur π-Conjugated Compounds 4,5-Vinylenedithio-1,3-dithiole-2-thione (C₅H₂S₅) and 4,5-Vinylenedithio-1,3-dithiole-2-one (C₅H₂OS₄)

Abstract

Both the title multi-sulfur molecules C₅H₂S₅ (1) and C₅H₂OS₄ (2) have a chair conformation, while molecule 1 has a higher degree of π-conjugation. Both the crystals are characterized by short S···S intermolecular contacts and by face-to-face column-like packing style, but crystal 1 has been more stabilized which may be the result of its stronger π–π intermolecular interactions. Compound 1 crystallizes in non-centrosymmetric polar space group Pmn2₁ with a = 10.6826(17), b = 9.3633(11), c = 4.0764(6) Å, V = 407.74(10) Å³, and Z = 2. The molecular dipole moment of 1 is ±62.5(1)° away from the macro-polarization direction along the c-axis. Consequently, the crystalline powder of crystal 1 exhibit a second harmonic generating (SHG) intensity 0.5 time strong as that of urea standard powder crystals when irradiated by a 1,080 nm of Nd:YAP laser beam. Compound 2 shows no SHG effect because it crystallizes in centrosymmtric space group Pbca with a = 11.4208(8), b = 7.8843(9), c = 33.587(3) Å, V = 3024.3(5) Å³, and Z = 16.

Index Abstract

Structures and Non-linear Optical Properties of Multi-Sulfur π-Conjugated Compounds 4,5-Vinylenedithio-1,3-dithiole-2-thione (C₅H₂S₅) and 4,5-Vinylenedithio-1,3-dithiole-2-one (C₅H₂OS₄)

Gang Xue, Qi Fang,* Wen-Tao Yu, Xia Chen, and Hong Lei

Compound C₅H₂S₅ crystallizes in the polar space group Pmn2₁ and its crystalline powder exhibits a second harmonic generating (SHG) intensity 0.5 times that of urea standard (1080 nm → 540 nm), while the similar compound C₅H₂OS₄ has no SHG effect because of its centrosymmetric space group Pbca.