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In manganese(III) complexes with BPh4− as the counter anion, the ligand field strength and non-covalent interactions between cations and anions of the flexible Schiff-base ligands (R-sal-N-1,5,8,12)2− are tuned by modifying the different substituents at the 5-position or 3,5-positions on the phenyl rings of the salicylaldehyde, and the magneto-structural properties of complexes 5-I-BPh4 (1), 5-tBu-BPh4 (2), 5-OCH3-BPh4 (3), naphth-BPh4 (4) and 5-Br-3-OCH3-BPh4 (5) are investigated. Complex 1 undergoes an incomplete SCO with two different Mn(III) sites, while complexes 2 and 3 remain in the HS state throughout the entire temperature range, suggesting the absence of magnetic state conversion. Under the effect of solvent, complex 4 shows different magnetic properties. Upon solvent loss, 4 displays a more complete SCO with a T1/2 of 140 K. In contrast to the complexes described above, complex 5 possesses two substituents, namely 5-Br and 3-OCH3. As a result, it exhibits an abrupt SCO effect due to the significantly stronger intermolecular cooperativity. [ABSTRACT FROM AUTHOR]

A series of Fe(III) complexes [Fe(5-F-sal-N-1,4,7,10)]Y (Y = PF6− for 1, Y = ClO4− for 2, Y = I− for 3 and Y = NO3− for 4) have been prepared. Single-crystal X-ray crystallographic studies show that complex 1 crystallizes in the orthorhombic Pna21 space group and complexes 2–4 have an isomorphous structure and crystallize in the same monoclinic space group, P21/n. Complexes 2–4 have two independent molecules (Fe1 and Fe2) in the unit cell. Magnetic susceptibility measurements demonstrated that complexes 1 and 3 showed a gradual one-step SCO behavior (T1/2 for 1 = 177 K and for 3 = 227 K) without thermal hysteresis. The magnetic behavior of 2 shows an incomplete two-step SCO process at T1/2 = 114 K and 170 K, respectively, while 4 is in a high-spin state at all measured temperatures. A careful evaluation of the supramolecular structures of these complexes revealed correlation between the supramolecular packing forces and their SCO behavior. The crystal structure of 1 consists of a three-dimensional (3D) extended network constructed from N–H⋯F and C–H⋯F hydrogen bonds, and C–H⋯π and C⋯C short contacts. In compounds 2–4, the crystal packing is governed by C⋯C, C–H⋯π and p–π interactions for the Fe1 centers and by C–H⋯π/O interactions for the Fe2 centers, which form 1D chains. Additional interactions (C–H⋯F and N–H⋯O/I) connect the neighboring chains and planes to form a complex supramolecular network. The anion⋯π interactions in 4 provide a means for preventing SCO occurring at low temperatures. This suggests that the supramolecular connectivity of the anions influences the magnetic properties. [ABSTRACT FROM AUTHOR]

The effect of counter anions on thermally induced manganese(III)-based SCO within the [Mn(5-F-sal-N-1,5,8,12)]Y family has been investigated. All the complexes are crystallized without any lattice solvents. Crystal packing and intermolecular forces influence the spin-state stabilization and spin-transition profiles. Magnetic measurements indicate that salts with octahedral anions, [Mn(5-F-sal-N-1,5,8,12)]PF6 (1), [Mn(5-F-sal-N-1,5,8,12)]AsF6 (2) and [Mn(5-F-sal-N-1,5,8,12)]SbF6 (3), show HS electronic configurations between 2 and 300 K, and there exist π–π stackings between the phenyl groups from the neighboring [Mn(5-F-sal-N-1,5,8,12)]+ cations. As for the tetrahedral anions, complex [Mn(5-F-sal-N-1,5,8,12)]BF4 (4) exhibits a gradual and incomplete spin conversion. Complex [Mn(5-F-sal-N-1,5,8,12)] ClO4 (5) shows a nearly complete SCO with T1/2 = 100 K. The remaining salts with spherical anions form Nam–H⋯X (X = Cl, Br, I) hydrogen bonds between Mn(III) cations and counterions. Complexes [Mn(5-F-sal-N-1,5,8,12)]Cl (6) and [Mn(5-F-sal-N-1,5,8,12)] Cl0.28Br0.72 (7) feature gradual SCO behaviors with T1/2 = 220 K and 235 K, respectively. Complex [Mn(5-F-sal-N-1,5,8,12)]I (8) exhibits a more gradual spin conversion and is far from a complete HS state with a χMT value of 1.89 cm3 mol−1 K at 400 K. [ABSTRACT FROM AUTHOR]

This paper reports the syntheses, crystal structures and magnetic properties of spin crossover (SCO) salts of formulae [Mn(naphth-sal-N-1,5,8,12)]SbF6 (1), [Mn(naphth-sal-N-1,5,8,12)]AsF6 (2), [Mn(naphth-sal-N-1,5,8,12)]PF6·1/2CH3OH (3) and [Mn(naphth-sal-N-1,5,8,12)]ClO4 (4), where (naphth-sal-N-1,5,8,12)2− (2,2′-((1E,14E)-2,6,10,14-tetraazapentadeca-1,14-diene-1,15-diyl)diphenolate) is a big conjugated hexadentate Schiff-base ligand. Magnetic susceptibility measurements demonstrated that complexes 1 and 2 showed a gradual one-step SCO between the high-spin (HS, S = 2) and low-spin (LS, S = 1) states without thermal hysteresis. The transition temperatures T1/2 of the SbF6 (1) and AsF6 (2) salts estimated from the magnetic susceptibility measurements are 164 and 171 K, respectively. The existence of the crystal solvent of complex 3 changes the supramolecular packing, leading to close π⋯π stacking interactions between the phenyl groups of the ligands. These close stacking interactions hinder the flexibility of the whole ligand, precluding the spin transformation of complex 3 and leading to its stabilization in the HS state in the temperature range of 2–300 K. For 4, crystal structure analysis indicates that the reduction in the anion size leads to close contacts between the naphthalene rings. These C–H⋯π interactions provide a means for preventing the spin crossover occurring at low temperatures. [ABSTRACT FROM AUTHOR]

Two novel phosphorescent Ir(III) complexes, Ir(fom)2(pic) and Ir(fof)2(pic), containing fluorene oxadiazole groups have been synthesized and characterized. The photophysical properties of the complexes have been investigated. Interestingly, both complexes exhibited aggregation-induced phosphorescent emission. The X-ray diffraction study showed that the AIPE properties resulted from weak π–π and C–H⋯N hydrogen-bonding interactions in the aggregated state restricting the rotation of the phenyl groups in the cyclometalating ligands. Owing to the sensitive and selective luminescence quenching of the complexes using picric acid (PA), the complexes were used for PA detection in aqueous media. Additionally, electroluminescence devices have been fabricated using the complexes at 5%–30% doping concentrations. The devices based on Ir(fof)2(pic) obtained the highest luminance 11 877 cd m−2 and current efficiency 23.2 cd A−1, which implied that the incorporation of fluorine could improve the electron affinity and ameliorate the capability of electron injection or transporting. [ABSTRACT FROM AUTHOR]

A series of Fe(III) complexes [Fe(5-F-sal-N-1,4,7,10)]Y (Y = PF 6 - for 1, Y = ClO 4 - for 2, Y = I - for 3 and Y = NO 3 - for 4) have been prepared. Single-crystal X-ray crystallographic studies show that complex 1 crystallizes in the orthorhombic Pna 2 1 space group and complexes 2-4 have an isomorphous structure and crystallize in the same monoclinic space group, P 2 1 / n . Complexes 2-4 have two independent molecules (Fe1 and Fe2) in the unit cell. Magnetic susceptibility measurements demonstrated that complexes 1 and 3 showed a gradual one-step SCO behavior ( T 1/2 for 1 = 177 K and for 3 = 227 K) without thermal hysteresis. The magnetic behavior of 2 shows an incomplete two-step SCO process at T 1/2 = 114 K and 170 K, respectively, while 4 is in a high-spin state at all measured temperatures. A careful evaluation of the supramolecular structures of these complexes revealed correlation between the supramolecular packing forces and their SCO behavior. The crystal structure of 1 consists of a three-dimensional (3D) extended network constructed from N-H⋯F and C-H⋯F hydrogen bonds, and C-H⋯π and C⋯C short contacts. In compounds 2-4, the crystal packing is governed by C⋯C, C-H⋯π and p-π interactions for the Fe1 centers and by C-H⋯π/O interactions for the Fe2 centers, which form 1D chains. Additional interactions (C-H⋯F and N-H⋯O/I) connect the neighboring chains and planes to form a complex supramolecular network. The anion⋯π interactions in 4 provide a means for preventing SCO occurring at low temperatures. This suggests that the supramolecular connectivity of the anions influences the magnetic properties.

Two novel phosphorescent Ir(iii) complexes, Ir(fom) 2 (pic) and Ir(fof) 2 (pic), containing fluorene oxadiazole groups have been synthesized and characterized. The photophysical properties of the complexes have been investigated. Interestingly, both complexes exhibited aggregation-induced phosphorescent emission. The X-ray diffraction study showed that the AIPE properties resulted from weak π-π and C-HN hydrogen-bonding interactions in the aggregated state restricting the rotation of the phenyl groups in the cyclometalating ligands. Owing to the sensitive and selective luminescence quenching of the complexes using picric acid (PA), the complexes were used for PA detection in aqueous media. Additionally, electroluminescence devices have been fabricated using the complexes at 5%-30% doping concentrations. The devices based on Ir(fof) 2 (pic) obtained the highest luminance 11 877 cd m -2 and current efficiency 23.2 cd A -1 , which implied that the incorporation of fluorine could improve the electron affinity and ameliorate the capability of electron injection or transporting.