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Two new mononuclear iron (II) coordination complexes: Fe(L1)2(SCN)2(1, L1:5-dimethylether-4-(4-methylphenyl)-3-(2-pyridinyl)-1,2,4-triazole) and Fe(L2)3(ClO4)2(2, L2:1-ethyl acetate-2-(2-pyridinyl)-imidazole), for the exploration of spin-crossover compounds have been synthesized and characterized. Structural analysis revealed that the framework of complex1is featured with 1-D chain structure connected by weak π···π interactions between the adjacent L1ligands, while complex2featured with various kinds of weak intermolecular hydrogen bonding interactions between Fe(L2)32+cation and ClO4−anion, which lead to a close crystal packing. The intermolecular interactions have shown a significant influence on the physical properties, and magnetic measurements of complexes1and2in the solid state at the room temperature revealed that the weak intermolecular interactions in1resulted in HS (high-spin) state, while the strong interactions in2lead to LS (low-spin) state over the whole temperature range. [ABSTRACT FROM PUBLISHER]

A series of Fe(II) complexes with (ClO4)−(SeCN)−, (ClO4)−(SCN)−, (Fe2OCl6)2−, and 2(BF4)−counter-anions for complexes1–4, derived from dmbpy (4,4′-dimethyl-2,2′-bipyridine), were prepared. The single-crystal studies and the Hirshfeld surfaces analysis revealed that the (Fe2OCl6)2−anion results more distortional octahedral geometry of the cation than other anions. In particular, the (ClO4)−(SCN)−and (Fe2OCl6)2−anions lead to complexes2and3stabilized via C-H···π interactions and π···π interactions, which were not found in the other two complexes. However, the double-chain structure of complex4was formed by C-H···F and C-H···C hydrogen bonds interactions. Due to the influence of different anions, magnetic susceptibility measurements showed that complex1was in high-spin (HS) state and complex2was in low-spin (LS) state. [ABSTRACT FROM PUBLISHER]

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]

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]

The complex [Cu2(μ-L)2]. DMF (L = 2, 2'-[1-(2, 4, 6-trichlorophenyl)-1H-1, 2, 4-triazole-3, 5-diyl] diphenolate) has been prepared and its structure determined. The two CuII ions are four-coordinated in a planar structure, with the DMF molecule wrapped in the 'wings' of ligand L. Hirshfeld surface and fingerprint plots reveal that the complex structure is stabilised mainly by H···H, C-H ... Cl, C-H···π,π···π and lone-pair···π (C-Cl) intermolecular interactions. [ABSTRACT FROM AUTHOR]

Four new complexes based on the 4-(4-carboxyphenyl)-1,2,4-triazole (Hcpt) ligand, {[Co(cpt) 2 (H 2 O) 4 ]·H 2 O}( 1 ), {[Cr(cpt) 2 (H 2 O) 4 ]·10H 2 O}( 2 ), {[Fe(cpt) 2 (H 2 O) 4 ]·10H 2 O}( 3 ), {[Zn(cpt) 2 (H 2 O) 2 ]}( 4 ) have been synthesized and characterized by elemental analysis, single crystal X-ray diffraction and TGA. For complexes 1 , 2 , and 3 , they almost have the same coordination mode that only one nitrogen atom of triazole are involved in the coordination, while in the complex 4 , only the group COO − participates in the coordination. In the crystal structure of 1 , each structural unit[Co(cpt) 2 (H 2 O) 4 ] is linked to another by hydrogen bonding formed by the lattice water molecules, thus forming a one-dimensional chain structure; In the crystal structure of 2 or 3, each structural unit[Cr(cpt) 2 (H 2 O) 4 ] or [Fe(cpt) 2 (H 2 O) 4 ] forms a two-dimensional layered structure by intermolecular hydrogen bonds from the coordinated water molecule and the group COO − . The results of thermogravimetric analysis show that the loss of lattice water and coordinated water molecules in 1 , 2 and 3 is below 120 °C, while the loss of coordinated water molecules in 4 is in the temperature range of 190–260 °C. Hirshfeld surface shows that the N H⋯O hydrogen bonding interaction plays a significant role towards the conformation of the basic structure of these complexes. [ABSTRACT FROM AUTHOR]

Four new complexes, [Co(dmbpy) 2 (dca) 2 ]·CH 3 OH ( 1 ), [Ni(dmbpy) 2 (dca) 2 ]·CH 3 OH ( 2 ), [Zn(dmbpy) 2 (dca) 2 ]·( 3 ) and [Cu(dmbpy) 2 (OH) 2 ]·5H 2 O ( 4 ) (dca = dicyanamide), derived from 4,4′-dimethyl-2,2′-bipyridine (dmbpy) have been synthesized and characterized by elemental analysis, TGA and single-crystal X-ray diffraction. Crystal structures and Hirshfeld surfaces analysis revealed that the complexes 1 – 3 were mainly supported by O H ⋯ N, C H ⋯ N and π ⋯ π intermolecular interactions, and for complex 4 , the uncoordinated water molecules play a key role in the construction of the 3D stacking motif. UV spectrum measurements demonstrate that all of the complexes show typical metal to ligand charge transfer (MLCT) absorption bands between 301 and 306 nm. Moreover, after complexation, the absorption maximum bands about intraligand π → π* transitions similarly show slightly red shift compared to dmbpy ligand, consisting with the DFT calculations. [ABSTRACT FROM AUTHOR]