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Investigations of spin-crossover in an iron(II) tris(diimine) system, based on the ligands L 1 (4,5-dimethy-2-(pyridine-2-yl)imidazole) and L 2 (1-acetic ethyl-2-(pyridine-2-yl)-imidazole), have been presented in this paper. The methyl groups at adjacent sites to the donor atoms in the ligand L 1 generated the crossover situation for complexes Fe( L 1 ) 3 (ClO 4 − ) 2 ( 1 ), Fe( L 1 ) 3 (BF 4 − ) 2 ( 2 ), Fe( L 1 ) 3 (PF 6 − ) 2 ( 3 ) and Fe( L 1 ) 3 (SbF 6 − ) 2 ( 4 ), while the acetic ethyl group at the non-coordinating NH site of the ligand L 2 resulted in an increase in the ligand field and generated a low-spin (LS) state for the complex Fe( L 2 ) 3 (ClO 4 − ) 2 ( 5 ). Complexes 1 and 5 were structurally characterized by single-crystal X-ray diffraction at different spin-states, while the phase purity of complexes 2 – 4 was confirmed by PXRD. Raman, IR and UV–Vis absorption spectra and magnetic properties of 1 – 4 were obtained, which revealed the influence of different counter anions on the spin transition temperatures. The blue-shift of IR and Raman spectra, red-shift and decrease in molar absorptivity of UV–Vis absorption spectra all follow the sequence 1 < 3 < 2 < 4 . [ABSTRACT FROM AUTHOR]

Five supramolecular assembly complexes: 2-hydroxypropane-1,3-diammonium-perchlorate-18-crown-6 ([C3H12N2O-(18-crown-6)2]2+·2[ClO4]−, 1); 2-hydroxypropane-1,3-diammonium-tetrafluoroborate-18-crown-6 ([(C3H12N2O)2-(18-crown-6)3]2+·2[BF4]−, 2); 4-methylanilinium perchlorate-18-crown-6 ([C7H10N-(18-crown-6)]+·[ClO4]−, 3); 4-iodineanilinium-tetrafluoroborate-18-crown-6 ([C6H7NI-(18-crown-6)]+·[BF4]−, 4); 4-methylanilinium tetrafluoroborate-18-crown-6 ([C7H10N-(18-crown-6)]+·[BF4]−, 5), for the investigation of the influence of different inorganic anions on the orientation of ammonium cation and host–guest interaction of crown ethers, have been synthesized and characterized. The results revealed that ClO4 − anion lead to the 2:1 composition of crown and ammonium cation in monoclinic space group and 3:2 composition of crown and ammonium cation in the presence of BF4 − anion for double-anilinium system (complexes 1 and 2). While for the single-anilinium system (complexes 3, 4, and 5), the different inorganic anions lead to quite different orientation of the ammoniums in orthorhombic space group. We also studied the TGA/DSC properties, Raman spectrascopy and hot stage microscopy for the five complexes. [ABSTRACT FROM AUTHOR]

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]

Fluorescent materials have many interesting applications, but it remains difficult to control the luminescence of organic materials and in particular to retain the same luminescence in solution and in the solid state, a property of interest for various imaging applications. In this work, the influence of inorganic-anions on the crystal structure and physical–chemical properties of a series organic salts L + Cl − ( 1 ), L + ClO 4 − ( 2 ), L + NO 3 − ·H 2 O ( 3 ), 2 L + SO 4 2− ·2H 2 O ( 4 ) ( L = 4-[(4H-1,2,4-triazol-4-ylimino)methyl]phenol) has been investigated. Single crystal X-ray analyzes revealed that salt 1 formed a linear structure connected by H⋯O interactions, while salts 2 – 4 all formed 2D network structures through O⋯O interactions. The protonated L + s adopt face-to-face slipped π-stacked arrangement in salts 1 and 3 , while display monomer arrangements in 2 and 4 , the latter can be attribute to the entrapment of heavy anions in the crystal lattices. Optical-properties measurements of these four salts have shown L + arrangements dependent on solid-state properties: salt 1 and 3 show broad emission bands ( λ 1 = 478 nm, λ 2 = 487 nm) with a red shift of about 60 nm relative to its fluorescence in solvents, while 2 and 4 are similar to each other, exhibiting sharp bands ( λ 3 = 453 nm, λ 2 = 433 nm) with the higher ϕ PL values ( ϕ PL1 = 0.08, ϕ PL1 = 0.15, ϕ PL1 = 0.06, ϕ PL1 = 0.14). These results demonstrated the significant influence of inorganic-anions on the organic salts and the optical properties of organic materials could be modulated by entrapping different anions in lattice. [ABSTRACT FROM AUTHOR]

In the present study, the assembly of 6-aminonicotinic acid with inorganic acids (HBr, HNO 3 and H 3 PO 4 ) has been performed, which resulted in the molecular salts C 6 H 7 N 2 O 2 + ·Br − ( 1 ), C 6 H 7 N 2 O 2 + ·NO 3 − ( 2 ) and C 6 H 7 N 2 O 2 + ·H 2 PO 4 − ( 3 ), respectively. These three molecular salts have been characterized by single-crystal X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) and UV–Vis absorption spectroscopy (UV). The results revealed that molecular salt 1 exhibits an infinite 1-D chain structure stabilized mainly by N–H⋯Br contacts, while 2 and 3 show a 2-D network and a 3-D stereoscopic framework, respectively, which are stabilized mainly by strong N–H⋯O hydrogen bonding contacts. Hirshfeld surface analysis demonstrated the presence of H⋯H, O–H⋯N, C–H⋯π and π⋯π intermolecular interactions. In addition, the UV–Vis spectra exhibit a slight blue-shift to a shorter wavelength, which suggests the clear influence of the inorganic anions. [ABSTRACT FROM AUTHOR]