Some viologen-containing compounds displaying thermo/photochromic behaviors which can be used as inkless print media and anti-counterfeiting materials have been reported.

Metallacrowns represent a new class of multinuclear clusters that are analogous to crown ethers in both structure and function. [1, 2] One may substitute heteroatoms, such as transition metals and nitrogen atoms, for the methylene carbon atoms of the parent ether complexes to form metallacrowns. There has been considerable interest in metallacrown chemistry owing to potential applications in chemically modified electrodes, anion-selective separation agents, liquid-crystal precursors, and magnetic materials. [3] Generally, the metallacrowns can be synthesized using either multidentate ligands that bridge two metal ions [4] or bridging chalcogen ligands, such as NaSR, [5] NaSeR, [6] and OR anions.[ (1), a novel [12]metallacrown-6 nickel cluster as shown by single-crystal X-ray diffraction. We repeated the experiment and were able to form this product in high yield. Herein we report the spontaneous self-assembly and crystal structure of compound 1 as well as investigations on its UV/Vis spectrum and thermal stability.The crystal lattice of compound 1 [8] is made up of a centrosymmetric [Ni 6 (SCH 2 CH 2 OH) 12 ] molecule (Figure 1). Each Ni atom is surrounded by four S atoms of the m 2 -SCH 2 CH 2 OH ligands in a distorted square-planar fashion. As a result, the edge-sharing NiS 4 planes connect to form a ring. The six nickel atoms approximately form a hexagon, with NiÀ Ni separations in the range of 2.9010(15)-2.9378(17) , vertex angles of 119.08(5)-121.38(5)8, and an average deviation of AE 0.001 from the best least-squares Ni 6 plane. The diameter of the ring, defined as the average distance between two opposing nickel atoms, is 5.84 . Two m 2 -S bridges

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Four tetranuclear 2-mercaptobenzothiazole cluster compounds [M 4 O(MBT) 6 ] (M = Fe, Co, Ni, Cu; MBT = 2-mercaptobenzhothiazole) were synthesized and characterized by elemental analyses, IR and UV-vis spectra, and single crystal X-ray crystallography. The crystal structures of [M 4 O(MBT) 6 ] (M = Fe, Co, Ni) confirm that the four metal(II) atoms locate four capsheaves of a tetrahedral skeletal structure and a tetracoordinate O 22 as an interstitial atom occupies the centre position of this tetrahedron. The metal atoms all possess slightly distorted tetrahedral geometry. The thermal gravimetry data indicate that these clusters all have good thermal stability. The nonlinear absorption of four cluster solutions (in DMF) were measured by open-aperture Z-scan technique at a 532 nm wavelength. The results of Z-scan experiments show that these clusters all have remarkable and very strong nonlinear optical absorption effects. The largest two-photon absorption cross-section is 172880 GM for cluster [Fe 4 O(MBT) 6 ].

Key indicatorsSingle-crystal X-ray study T = 295 K Mean (C-C) = 0.003 Å R factor = 0.048 wR factor = 0.160 Data-to-parameter ratio = 16.2 For details of how these key indicators were automatically derived from the article, see

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