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Pyridin-4-ylmethanaminium perchlorate monohydrate (synonym: 4-picolyl­ammonium perchlorate monohydrate), C6H9N2+·ClO4−·H2O, crystallizes in the monoclinic system (space group P21/n) with the asymmetric unit comprising two formula units (Z′ = 2). All mol­ecular entities are located on general positions. The two crystallographically distinct 4-picolyl­ammonium cations exhibit different conformations. The two unique perchlorate anions are non-disordered, showing an r.m.s. deviation of 0.011 Å from mol­ecular Td symmetry. The supra­molecular structure in the solid state features an intricate tri-periodic network of N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds.

8-Nitro-4H-benzo[e][1,3]thiazinones (BTZs) are potent in vitro antimycobacterial agents. New chemical transformations, viz. dearomatization and decarbonylation, of two BTZs and their influence on the compounds’ antimycobacterial properties are described. Reactions of 8-nitro-2-(piperidin-1-yl)-6-(trifluoromethyl)-4H-benzo[e][1,3]thiazin-4-one and the clinical drug candidate BTZ043 with the Grignard reagent CH3MgBr afford the corresponding dearomatized stable 4,5-dimethyl-5H- and 4,7-dimethyl-7H-benzo[e][1,3]thiazines. These methine compounds are structurally characterized by X-ray crystallography for the first time. Reduction of the BTZ carbonyl group, leading to the corresponding markedly non-planar 4H-benzo[e][1,3]thiazine systems, is achieved using the reducing agent (CH3)2S ⋅ BH3. Double methylation with dearomatization and decarbonylation renders the two BTZs studied inactive against Mycobacterium tuberculosis and Mycobacterium smegmatis, as proven by in vitro growth inhibition assays.

(Z)-1,2-Bis[4-oxo-2-(piperidin-1-yl)-6-(tri­fluoro­meth­yl)-4H-benzo[e][1,3]thiazin-8-yl]diazene oxide, C28H24F6N6O3S2, was obtained and its structure determined while attempting to crystallize and structurally characterize 8-nitro-2-(piperidin-1-yl)-6-(trifluoro­meth­yl)-4H-benzo[e][1,3]thia­zin-4-one, a simplified analogue of the antituberculosis clinical drug candidate BTZ043. X-ray crystallography revealed the structure of the az­oxy compound to be comprised of two benzo­thia­zinone moieties linked by a Z-configured az­oxy group in an almost coplanar arrangement. In the crystal, the mol­ecules are densely packed, revealing a herringbone pattern.

Zinc–zinc interactions on nickel and palladium centers are highly dependent on the co-ligands. These dependencies are also found for the formation of dihydrogen vs. dihydride complexes and underline the analogy [Zn2Cp*2] ↔ H2., The analogy between ZnR fragments and the hydrogen radical represents a fruitful concept in organometallic synthesis. The organozinc(ii) and -zinc(i) sources ZnMe2 (Me = methyl) and [Zn2Cp*2] (Cp* = pentamethylcyclopentadienyl) provide one-electron fragments ·ZnR (R = Me, Cp*), which can be trapped by transition metal complexes [LaM], yielding [Lb(ZnR)n]. The addition of the dizinc compound [Zn2Cp*2] to coordinatively unsaturated [LaM] by the homolytic cleavage of the Zn–Zn bond can be compared to the classic oxidative addition reaction of H2, forming dihydride complexes [LaM(H)2]. It has also been widely shown that dihydrogen coordinates under preservation of the H–H bond in the case of certain electronic properties of the transition metal fragment. The σ-aromatic triangular clusters [Zn3Cp*3]+ and [Zn2CuCp*3] may be regarded as the first indication of this so far unknown, side-on coordination mode of [Zn2Cp*2]. With this background in mind the question arises if a series of complexes featuring the Zn2M structural motif can be prepared exhibiting a (more or less) intact Zn–Zn interaction, i.e. di-zinc complexes which are analogous to non-classical dihydrogen complexes of the Kubas type. In order to probe this idea, a series of interrelated organozinc nickel and palladium complexes and clusters were synthesized and characterized as model compounds: [Ni(ZnCp*)(ZnMe)(PMe3)3] (1), [Ni(ZnCp*)2(ZnMe)2(PMe3)2] (2), [{Ni(CNtBu)2(μ2-ZnCp*)(μ2-ZnMe)}2] (3), [Pd(ZnCp*)4(CNtBu)2] (4) and [Pd3Zn6(PCy3)2(Cp*)4] (5). The dependence of Zn···Zn interactions as a function of the ligand environments and the metal centers was studied. Experimental X-ray crystallographic structural data and DFT calculations support the analogy between dihydrogen and dizinc transition metal complexes.

Acta crystallographica / C 72(11), 861 - 866(2016). doi:10.1107/S2053229616015515, Porphyrin assemblies display inter­esting photophysical properties and a relatively high thermal stability. Moreover, meso-functionalized porphyrins with virtually fourfold symmetry can be relatively readily synthesized from pyrrole and the appropriate aldehyde. A number of metallo derivatives of 5,10,15,20-tetra­kis­(4-cyano­phen­yl)porphyrin, where the N atom of the linear cyano group can act both as a donor for coordination bonds or as an acceptor for hydrogen bonds, have been structurally characterized by single-crystal X-ray analysis. The supra­molecular and structural chemistry of the corresponding 2- and 3-cyano­phenyl isomers of the parent porphyrin, however, has remained largely unexplored. The crystal structure of [5,10,15,20-tetra­kis­(3-cyano­phen­yl)porphyrinato]copper(II) (CuTCNPP) nitro­benzene tris­olvate, [Cu(C$_{48}$H$_{24}$N$_8$)]·3C$_6$H$_5$NO$_2$, has been determined at 80 K by synchrotron single-crystal X-ray diffraction. CuTCNPP exhibits a C$_{2h}$-symmetric $\alpha\alpha^{\beta\beta}$ conformation, despite an unsymmetrical crystal environment, and is situated on a crystallographic centre of symmetry. The Cu$^{II}$ ion adopts a genuine square-planar coordination by the four pyrrole N atoms. The 24-membered porphyrin ring system shows no marked deviation from planarity. In the crystal, the CuTCNPP mol­ecules and two nitro­benzene mol­ecules are face-to-face stacked in an alternating fashion, resulting in corrugated layers. The remaining nitro­benzene guest mol­ecule per CuTCNPP resides in the region between four neighbouring columnar stacks of CuTCNPP and sandwiched nitro­benzene mol­ecules, and is disordered over four positions about a centre of symmetry., Published by Wiley-Blackwell, Oxford

International audience; The first example of ligand protected Cu-Zn clusters is described. Reaction of [CpCu(CN(t)Bu)] with [Zn2Cp*2] yields [(CuCN(t)Bu)4(ZnCp*)4] (1a) and [(CuCN(t)Bu)4(ZnCp*)3(ZnCp)] (1b). According to DFT calculations, the [Cu4Zn4] unit fulfils the unified superatom model for cluster valence shell closing.