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Investigation of spin-crossover in iron(II)-di(diamine) system, based on ligands L 1 , 4,5-dimethy-2-(pyridine-2-yl)imidazole, has been presented in this paper. The methyl group at the adjacent sites of the donor atoms in ligand L 1 can generate the crossover situation for the iron(II) tris(diimine) system. While for the iron(II)-di(diamine) system with L 1 , the results are complicated: complex 1 {Fe( L 1 ) 2 (SCN) 2 } displays paramagnetic behavior while 2 {Fe( L 1 ) 2 (SeCN) 2 } is in crossover situation. The difference was attributed to the various ligand field strength of SCN − and SeCN − , which also resulted to the blue-shift of IR and Raman spectra, as well as red-shift and decrease in molar absorptivity of UV–Vis absorption spectrum. [ABSTRACT FROM AUTHOR]

Guest molecule dependent crystal structures, intermolecular interactions and magnetic properties of an iron (II) coordination polymer ( 2 ) with 4,4′-dipyridyl disulfide (4-DPS) ligand have been investigated. Polymer 2 {[Fe(NCS) 2 (4-PDS) 2 ]·2(2,5-DCP)} n was derived from polymer 1 [Fe(NCS) 2 (4-PDS) 2 ·4H 2 O] n through the change of water molecules by 2,5-dichloropyrazine molecules (2,5-DCP). This substitution leads to the change of the polymer motif from di -triangle to rectangle, and the decrease of longer contacts (S–H, N–H, C–H and H–H) while increase of the π ⋯ π (C–C) contacts in the crystal. These above changes then tuned the electronic structure of the iron (II) ion from high spin (HS) state ( 1 ) to the onset high spin (HS)–low spin (LS) transition ( 2 ), and resulted intermolecular anti-ferromagnetic interactions at lower temperatures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two new complexes from 6-methylnicotinic acid (6-MNA) have been presented. [•] Influences of metals on 6-MNA through Hirsheld surfaces have been investigated. [•] Intermolecular interactions of complexes have been quantificationally visualized. [ABSTRACT FROM AUTHOR]

Highlights: [•] The fourth CuII–azido-pyrazine complex has been synthesised and characterized. [•] The crystal structure display novel 3D-42.63.8-topology with 2D honeycomb layer. [•] The complex exhibit strong antiferromagnetic coupling. [ABSTRACT FROM AUTHOR]

Abstract: A novel N-donor bridging receptor R : 4,4′-methanediylbis(2-ethyl-5-methyl-1H-imidazole) has been synthesized from 2-ethyl-4-methyl-1H-imidazole and formaldehyde in the presence of potassium hydroxide. This receptor then formed complexes with different transition metals ([Co(NO3)2, CoCl2, Ni(NO3)2 and CuCl2]) in different solvent systems and obtained five different complexes. Wherein, the complex formation of R with Co(NO3)2 resulted in two different structures in methanol and acetonitrile, respectively. A thorough structural investigation of the present receptor and the resulted five complexes show that the NH group of the receptor, the organic anions and solvent molecules play a key role in the construction of the five intriguing architectures. We also prepared molecular Hirshfeld surface and fingerprint plot for R as well as the five complexes, which revealed the influences of different metals to the coordinate behavior of R in terms of intermolecular interactions. [Copyright &y& Elsevier]

Two zinc (II) pseudo-halide complexes [Zn( L 1 )(N 3 ) 2 ] n ( 1 L 1 : 1,2-diaminocyclohexane) and Zn( L 2 ) 2 (N 3 ) 2 ( 2 L 2 : 4,5-dimethy-2-(pyridine-2-yl) imidazole) have been synthesized and characterized. Single-crystal X-ray structural analysis revealed that the central Zn II atoms in 1 displays distorted trigonal bipyramidal arrangement with a 1D chain structure bridged by N 3 − anions, while in 2 , the central Zn II atoms incorporating with two bidentate L 2 ligands, and adopts an octahedral geometry and shows a “butterfly” coordination framework. Structural analysis demonstrated that the organic ligands play an important role in determining the resultant structure. In addition, both complexes were further characterized by thermal stability properties and Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]