A Domino Fusion of an Organic Ligand Depended on Metal-Induced and Oxygen Insertion, Unraveled by Crystallography, Mass Spectrometry, and DFT Calculations.

Herein, the reaction of (1-methyl-1 H-benzo[d]imidazol-2-yl)methanamine (L1) with Co(H O) Cl , in CH CN at 120 °C, leading to the 2,3,5,6-tetrakis(1-methyl-1 H-benzo[d]imidazol-2-yl)pyrazine (3), isolated as a dimeric cluster {[Co (3)Cl ]⋅2 CH CN} (2), is reported. When O and H O are present, (1-methyl-1 H-benzo[d]imidazole-2-carbonyl)amide (HL1') is first formed and crystallized as [Co (L1) (L1')]Cl ⋅2 H O (4) before fusion of HL1' with L1, giving 1-methyl-N-(1-methyl-1 H-benzo[d]imidazol-2-carbonyl)-1 H-benzo[d]imidazol-2-carboxamide (HL2'') forming a one-dimensional (1D) chain of [Co (L2'') Cl ] (5). The combination of crystallography and mass spectrometry (ESI-MS) of isolated crystals and the solutions taken from the reaction as a function time reveal seven intermediate steps leading to 2, but six steps for 5, for which a different sequence takes place.

Tracking the formation of a polynuclear Co16 complex and its elimination and substitution reactions by mass spectroscopy and crystallography.

We present the syntheses and structures of the biggest chiral cobalt coordination cluster, [Co16(L)4(H3L)8(N3)6](NO3)2·16H2O·2CH3OH (1, where H4L = S,S-1,2-bis(1H-benzimidazol-2-yl)-1,2-ethanediol). 1 consists of two Co4O4 cubes (Co4(L)2(H3L)2) alternating with Co2(EO-N3)2Co2 (Co4(L)2(H3L)2(N3)2), bridged by the benzimidazole and azide nitrogen atoms to form a twisted ring. The ligand adopts both cis and trans forms, and all the rings have the same chiralilty.

[Excitation-wavelength dependent photoluminescence from porous silicon].

With the technique of fluorescence spectral analysis, the dependence of the fluorescence from porous silicon on the excitation wavelength was investigated. It was found when the excitation wavelength decreases from 650 to 340 nm, the fluorescence spectrum of porous silicon blue shifts continuously from 780 to 490 nm. Using scanning electron microscopy (SEM) and computer simulation, the cross-sectional structures of porous silicon were studied.