W.F. Guo

Synthesis, crystal structure and saturable absorption in the near-IR regions of a new copper complex of dmit: hexadecyltrimethylammonium bis (2-thioxo-1,3-dithiole-4,5-dithiolato)-copper

A new copper complex of dmit, hexadecyltrimethylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)-copper([C16H33(CH3)3N][Cu(dmit)2], abbreviated as CTCU, C16H33(CH3)3N = hexadecyltrimethylammonium, dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate) has been synthesized and its structure determined by X-ray diffraction. The saturable absorption of CTCU at 1053 nm shows promise as a Q-switch dye in the near IR regions.

Bis(N-methylpyridinium) bis(2-thioxo-1,3-dithiole-4,5-dithiolato)zincate(II)

The crystal structure of (I) consists of [Zn(dmit)2] 2 anions and ethylpyridinium cations (Fig. 1). The anion has C2 symmetry. The Zn ion is located on a twofold axis and coordinated by four S atoms from two dmit ligands with a distorted tetrahedral geometry (Table 1). The dihedral angle between dmit planes is 69.44 (18) . The Zn ion deviates from each dmit mean plane by 0.230 (1) Å. Both independent cations have mirror symmetry, with the ethyl C atoms, pyridine N atoms, and atoms C5 and C13 lying on the mirror planes. In the crystal structure of (I), the S2 S2 separation of 3.6304 (13) Å [symmetry code: (iii) 12 x,1/2 y,1 z] is much longer than 3.492 (2) Å found in a similar compound, bis(N-methylpyridinium)[Zn(dmit)2] (Wang et al., 2005), and indicates the normal van der Waals contact between S atoms.

4,5-Bis(furoylsulfanyl)-1,3-dithiole-2-thione

The title compound, C13H6O4S5, possesses crystallographically imposed mirror symmetry, with the atoms of the C=S group lying on the mirror plane. It is an example of the general formula [RCO]2(dmit), where R is a furan ring and dmit is 2-thioxo-1,3-dithiole-4,5-dithiolate. The components exhibit some polarization of their molecular-electronic structure. The dmit and furan moieties exhibit a high degree of conjugation, as the introduction of C=O connecting the conjugated furan (donor) and dmit (acceptor) rings forms a good conjugated system with high delocalization. A polar three-dimensional framework is built from a combination of intermolecular contacts, namely SS interactions and C-HO hydrogen bonding. The structural characteristics lead to good second-order non-linear optical properties.

Third-order optical nonlinearity of a novel material : [ (C4H9)4N] [Co (dmit )2]

A novel dmit organometallic complex—[(C4H9)4N][Co(dmit)2] (dmit2− = 4,5-dithiolate-1,3-dithiole-2-thione), abbreviated as BuCo, is synthesized and its third-order optical nonlinearity of the acetone solution is characterized using the Z-scan technique with a 40-ps pulse width at 1064 nm. Z-scan curves show that BuCo sample solution possesses the negative nonlinear refraction, exhibiting a self-defocusing effect. In addition, the two-photon absorption has been observed in BuCo. The effective molecular second-order hyperpolarizability γeff of the BuCo molecule was estimated to be as large as 5.60 × 10−31 esu, suggesting BuCo is a potential material for optical device applications.

Investigation of growth modes of manganese mercury thiocyanate crystal by atomic force microscopy

The growth mechanism and defect formation of the {110} faces of manganese mercury thiocyanate crystals were investigated by atomic force microscopy. A dislocation-controlled mechanism and a two-dimensional nucleation mechanism operate simultaneously during growth. Previous observations showed that two-dimensional nuclei appeared at interstep terraces of spiral hillocks. In this work, it is found for the first time that layers of two-dimensional islands cover up the outcrops of screw dislocations. The spiral hillocks grow fast along the (114) directions, which is probably due to the small interplanar distances of the {114} faces. Two-dimensional islands often appear as pairs of islands of nearly the same size, at the larger step terraces. Crystallization of the liquid inclusions occurs during the separation of the sample from the mother solution. Small three-dimensional islands, in high density, induce extra stress, which subsequently generates after-growth dislocations.

Nonlinear optical studies of an organo-metallic complex by Z-scan technique

The nonlinear optical properties of an organo-metallic compound, tetrabutylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurum, abbreviated as BuAu, are investigated by Z-scan technique with 28 ps pulse width at 532 nm. Strong reverse saturable absorption has been found, the effective excited-state absorption cross section is obtained as σeff = 1.818×10-17 cm2. The material also shows self-defocus and the nonlinear optical refractive index is measured as n2 = -1.341×10-12 esu with the concentration of 2×10-3 mol/L. All the results suggest that this material has potential application as optical devices.

GROWTH MORPHOLOGY OF THE {100} CLEAVAGE FACES OF LAP CRYSTALS OBSERVED BY AFM

Morphology of the {100} cleavage faces of L-arginine phosphate monohydrate single crystal before and after its growth at 40°C at a supersaturation of 0.031 has been studied. Monolayer and multilayer steps are found on the original cleaved surfaces. The regrowth morphology varies in nature with different growth time. With the increase of the growth time more growth layers and two-dimensional nucleus come into being, and they become more stable.