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A mononuclear complex with long alkyl chains, [FeII(H2Bpz2)2(C9bpy)] (1; H2Bpz2 = dihydrobis(1-pyrazolyl)borate, C9bpy = 4,4′-dinonyl-2,2′-bipyridine), was synthesized. Single-crystal X-ray crystallographic studies revealed that the Δ- and Λ-forms of the complex co-crystallized in the lattice asymmetric unit, while magnetic measurements unveiled that this complex underwent incomplete one-step spin crossover (SCO) with the transition completeness and temperature depending on the measurement velocity because of slow spin equilibrium. Multivariable approaches such as varying scan rate, annealing the sample, light irradiation and pressure have been adopted to effectively overcome the slow spin equilibrium and thus improve the SCO completeness. [ABSTRACT FROM AUTHOR]

Hofmann-type spin-crossover (SCO) frameworks attract much attention due to their predictable structures and diverse SCO behaviours. In this paper, we report two isostructural two-dimensional (2D) Hofmann-type SCO frameworks [FeII(ppe)2MII(CN)4]·3H2O (ppe = 1-(2-pyridyl)-2-(4-pyridyl)ethylene and M = Pd for 1 and Pt for 2). X-ray crystallographic studies, magnetic measurements and Mössbauer spectra jointly reveal that both compounds undergo complete hysteretic two-step SCO, i.e. HS1.0 HS0.6–0.5LS0.4–0.5 LS1.0 conversion with thermal hysteresis loops of 14 K and 28 K wide for 1 and 13 K and 26 K wide for 2. The dehydrated samples, 1-dehydrated and 2-dehydrated, display different SCO behaviours, unveiling that the SCO behaviours are affected by guest water molecules. [ABSTRACT FROM AUTHOR]

The development of molecular materials whose physical properties can be switched between different states has attracted significant attention for their potential application in sensing, information processing, spintronics, and smart actuators. Generally speaking, such functional bistability can be induced by the motion of electrons or constituted molecules in response to external stimuli. In this Feature Article, we will introduce how to manipulate the structural variations, including spin crossover, molecular reorientation, and molecular displacement, to tune the magnetic properties, optical properties, dielectric properties, and mechanical response of single-crystal materials, with a highlight of our contributions to this booming field. [ABSTRACT FROM AUTHOR]

Correction for 'Multiple correlations between spin crossover and fluorescence in a dinuclear compound' by Chun-Feng Wang et al., Chem. Commun., 2016, 52, 14322–14325, https://doi.org/10.1039/C6CC07810A. [ABSTRACT FROM AUTHOR]

Three one-dimensional looped coordination polymers with the formula of [Fe(dpds)2{C(CN)3}2]·dpds (1, dpds = 4,4′-dipyridyl disulfide), [Fe(dpds)2(NCBH3)2] (2) and [Fe(dpds)2(NCSe)2]·3.5H2O (3) have been synthesized and characterized by single-crystal X-ray crystallography, Mössbauer spectroscopy and magnetic measurements. The spin-crossover (SCO) behaviors of these compounds depend significantly on axial ligands: compound 1 exhibited thermal-induced complete one-step SCO behavior with a T1/2 of 170 K, and 2 showed incomplete SCO behavior with T1/2 being 130 K, whereas 3 was paramagnetic. Meanwhile, both compounds 1 and 2 displayed light-induced excited spin-state trapping (LIESST) effects, featuring TLIESST values of 45 K and 61 K for 1 and 2, respectively, which were independent of exciting laser wavelengths. These results suggest that anions such as C(CN)3− and NCBH3− with much stronger ligand fields are needed in order to realize spin-state switching, if a ligand such as dpds is adopted to synthesize SCO compounds. [ABSTRACT FROM AUTHOR]

A novel bent ligand-pillared three-dimensional Hofmann-type metal–organic framework, [FeII(Hbpt)Pt(CN)4]·1/2Hbpt·1/2CH3OH·5/2H2O [1, Hbpt = 4,4′-(1H-1,2,4-triazole-3,5-diyl) dipyridine], was synthesized and crystallographically and magnetically characterized, which showed incomplete three-step spin-crossover behavior with a reversible three equal-step sequence of HS1.00↑ HS0.75LS0.25↑ HS0.5LS0.5↑ HS0.25LS0.75. [ABSTRACT FROM AUTHOR]

Multiple correlations between spin crossover and fluorescence are established in a dinuclear compound with fluorescence from d(Fe) + π(SCN) to π*(ligand) charge transfer and correlation originated from ligand to Fe(ii) energy transfer. [ABSTRACT FROM AUTHOR]

The reactions of tricyanometallate precursors, (Ph3PMe)[(Tp4-Me)Fe(CN)3·0.5CH3CN] (1) (Tp4-Me = tri(4-methyl-pyrazol-1-yl)borate) and (NBu4)[(MeTp)Fe(CN)3] (MeTp = methyltris(pyrazolyl)borate) with the presence of the tetradentate tpa ligand (tpa = tris(2-pyridylmethyl)amine) and Fe(ClO4)2·6H2O afford two new cyano-bridged mixed-valence {FeIII2FeII2} molecular squares: [(Tp4-Me)FeIII(CN)3]2[FeII(tpa)]2·2ClO4·H2O (2·H2O) and [(MeTp)FeIII(CN)3]2[FeII(tpa)]2·2ClO4·CH3OH (3·CH3OH). Solvent-exchange compounds of 3·CH3OH, [(MeTp)FeIII(CN)3]2[FeII(tpa)]2·2ClO4·2H2O (3·2H2O), and their solvent-free form (2 and 3) are also obtained, respectively. The spin crossover (SCO) properties of all compounds are confirmed by detailed structural analyses of the coordination environments of the FeII centres and magnetic susceptibility measurements. All compounds exhibit SCO behaviour near room temperature (T1/2 = 320 K for 2·H2O; 302 K for 2; 292 K for 3·CH3OH; 306 K for 3·2H2O and 290 K for 3) and reversible single-crystal to single-crystal (SC–SC) transformations induced by guest desorption and resorption or solvent exchange. The transition temperature close to room temperature can be tuned by the dehydration and re-hydration processes. The structure–property analysis discloses that the distorted {Fe4(μ-CN)4} core and deviations of bent 〈Fe−N≡C angles play a key role in tuning the transition temperature of these similar mixed-valence {FeIII2FeII2} complexes. [ABSTRACT FROM AUTHOR]

A 3D 2-fold interpenetrated porous coordination polymer, [Fe(NCS)2(tppm)]·5CH3OH·2CH2Cl2 (1·sol, tppm = 4,4′,4′′,4′′′-tetrakis(4-pyridylethen-2-yl)tetraphenylmethane), was synthesized, which showed temperature, light and solvent-induced spin-crossover behaviours. [ABSTRACT FROM AUTHOR]

A metal–organic framework, [{Fe(NCS)2}3(TPB)4]·x(guest) [1·x(guest), TPB = 1,3,5-tris(4-pyridyl)benzene], shows selective gas adsorption and guest-dependent spin-crossover behaviour. [ABSTRACT FROM AUTHOR]