Crystal Structure and Hirshfeld Surface Analysis of Bis(3-thienoyl) Disulfide

The spectroscopic characterization (¹H, ¹³C{¹H} NMR, UV–Vis) and single-crystal X-ray diffraction (scXRD) analysis accomplished by inspection of the Hirshfeld surface of bis(3-thienoyl) disulfide (1) is described. The title compound 1 crystallizes in the monoclinic space group P2₁/n. The unit cell parameters are a?=?7.9959(3) Å, b?=?6.4348(3) Å, c?=?22.4924(9) Å, β?=?100.108(4)°, V?=?1139.32(8) ų, Z?=?4, R_gt(F)?=?0.0278, wR_ref(F²)?=?0.0667. The packing of 1 is dominated by S?O and S?S interactions, giving a 2D layer structure parallel to (101). The X‐ray crystal structure analysis revealed the packing of 1 is dominated by S?O and S?S interactions, giving a 2D layer structure parallel to (101). The intermolecular interactions in 1 were analyzed using the Hirshfeld surface method including 2D fingerprint plots and enrichment ratios (E), which shows that the most favored intermolecular contacts are the O?H and C?S indicated by E values above 1.30. The interaction energies between molecular pairs revealed the importance of the weak O?H and C?S interactions in stabilizing the molecular structure of 1.

Graphic Abstract

Single crystal X-ray structure analysis, DFT calculations and Hirshfeld surface analysis to identify intermolecular interactions within the solid state structure of bis(3-thienoyl) disulfide (1).

     

Reversible intramolecular C-C bond formation/breaking and color switching mediated by a N,C-chelate in (2-ph-py)BMes2 and (5-BMes2-2-ph-py)BMes2

A diboron compound with both 3-coordinate boron and 4-coordinate boron centers, (5-BMes2-2-ph-py)BMes2 (1) and its monoboron analogue, (2-ph-py)BMes2 (2) have been synthesized. Both compounds are luminescent but have a high sensitivity toward light. UV and ambient light cause both compounds to isomerize to 1a and 2a, respectively, via the formation of a C-C bond between a mesityl and the phenyl group, accompanied by a drastic color change from yellow or colorless to dark olive green or dark blue. The structures of 1a and 2a were established by 2D NMR experiments and geometry optimization by DFT calculations. Both 1a and 2a can thermally reverse back to 1 and 2 via the breaking of a C-C bond, with the activation barrier being 107 and 110 kJ/mol, respectively. The N,C-chelate ligands in 1 and 2 were found to play a key role in promoting this unusual and reversible photo-thermal isomerization process on a tetrahedral boron center. Reactions with oxygen molecules convert 1a and 2a to 5-BMes2-2-[(2-Mes)-ph]-pyridine (1b) and 2-(2-Mes)-ph-pyridine (2b), respectively.