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The design of magnetic molecular materials exhibiting multiple functions has garnered significant interest owing to their potential applications in molecular switches, sensors, and data storage devices. In this study, we synthesized a two-dimensional (2D) FeII-based Hofmann-type coordination polymer, namely {Fe(DPPE)2[Ag(CN)2]2}·2EtOH (1), using a luminescent ligand 1,1-diphenyl-2,2-di(4-pyridylbiphenyl)ethylene (DPPE). Single-crystal structural analyses and magnetic measurements revealed a thermally induced spin crossover (SCO) with the transition temperature T1/2 = 231 K. Variable-temperature fluorescence emission spectra indicated the coexistence of spin crossover and fluorescence properties. Moreover, a pronounced dielectric change (Δε′ = 1.2 at 0.5 kHz) was observed during the SCO process, confirming the simultaneous magnetic and dielectric switching arising from the rearrangement of 3d electrons and deformation of the FeII-centered coordination sphere. This work provides an approach to explore the interplay between magnetic, dielectric, and fluorescence properties, and holds significance for developing multifunctional molecular materials. [ABSTRACT FROM AUTHOR]

The modular construction method provides a feasible way to construct pre-designed cyano-bridged {LnIIIMIV/V} systems with more attractive structures and adjustable interactions between 4d/5d and 4f ions. In this work, the pentadentate Schiff-base ligands H2Ln (H2L1: 2,6-diacetylpyridine bis(nicotinoylhydrazone); H2L2: 2,6-diacetylpyridine bis(isonicotinoylhydrazone)) with multiple coordination sites were designed to coordinate with DyIII ions firstly, and then combined with K4M(CN)8·2H2O (M = W, Mo) by a liquid–liquid diffusion method to successfully synthesize two trinuclear structures {Dy[MIV(CN)8]0.5(HL1)(H2O)3}2·8H2O (1: M = W; 2: M = Mo), and two dinuclear structures {[Dy[MIV(CN)8](H3L2)(H2O)3]}·sol (3: M = W, sol = 11.5H2O; 4: M = Mo, sol = 2CH3OH·9.5H2O). Interestingly, deprotonation occurs in ligand H2L1 during the formation of complexes 1 and 2, while deprotonation/protonation processes both occur in ligand H2L2 during the synthesis of complexes 3 and 4. Magnetic analyses reveal that complexes 1–4 are all field-induced single-ion magnets (SIMs). The energy barriers (Ueff/kB) of complexes 1 and 2 are 92.83 K and 101.08 K, respectively, which are nearly three-fold higher than those of complexes 3 (30.19 K) and 4 (32.77 K). Ab initio calculations were performed on these series of {LnIIIMIV} heteronuclear complexes to provide more insights into the magnetic relaxation properties. This work provides another example of improving the SMM behaviors of cyano-bridged {LnIIIMIV} systems by deprotonation/protonation at different sites in the ligands. [ABSTRACT FROM AUTHOR]

Cyano‐bridged 4d–4f molecular nanomagnets have re‐called increasing research interests in molecular magnetism since they offer more possibilities in achieving novel nanomagnets with versatile structures and magnetic interactions. In this work, four β‐diketone ligands bearing different substitution N‐sites were designed and synthesized, namely 1‐(2‐pyridyl)‐3‐(3‐pyridyl)‐1,3‐propanedione (HL1), 1,3‐Bis (3‐pyridyl)‐1,3‐propanedione (HL2), 1‐(4‐pyridyl)‐3‐(3‐pyridyl)‐1,3‐propanedione (HL3), and 1,3‐Bis (4‐pyridyl)‐1,3‐propanedione (HL4), to tune the magnetic relaxation behaviors of cyano‐bridged {DyIIIMoV} systems. By reacting with DyCl3 ⋅ 6H2O and K4Mo(CN)8 ⋅ 2H2O, four cyano‐bridged complexes, namely {[Dy[MoV(CN)8](HL1)2(H2O)3]} ⋅ 6H2O (1), {[Dy[MoV(CN)8](HL2)(H2O)3(CH3OH)]}2 ⋅ 2CH3OH ⋅ 3H2O (2), {[Dy[MoV(CN)8](HL3)(H2O)2(CH3OH)] ⋅ H2O}n (3), and {[Dy[MoV(CN)8](HL4)2(H2O)3]} ⋅ 2H2O⋅CH3OH (4) were obtained. Structural analyses revealed that 1 and 4 are binuclear complexes, 2 has a tetragonal structure, and 3 exhibits a stair‐like polymer chain structure. The DyIII ions in all complexes have eight‐coordinated configurations with the coordination spheres DyO7N1 for 1 and 4, DyO6N2 for 2, and DyO5N3 for 3. Magnetic measurements indicate that 1 is a zero‐field single‐molecule magnet (SMM) and complexes 2–4 are field‐induced SMMs, with complex 4 featuring a two‐step relaxation process. The magnetic characterizations and ab initio calculations revealed that changing the N‐sites in the β‐diketone ligands can effectively alter the structures and magnetic properties of cyano‐bridged 4d–4f nanomagnets by adjusting the coordination environments of the DyIII centers. [ABSTRACT FROM AUTHOR]

Colossal and anisotropic thermal expansion is a key function for microscale or nanoscale actuators in material science. Herein, we present a hexanuclear compound of [(Tp*)FeIII(CN)3]4[FeII(Ppmp)]2⋅2 CH3OH (1, Tp*=hydrotris(3,5‐dimethyl‐pyrazol‐1‐yl)borate and Ppmp=2‐[3‐(2′‐pyridyl)pyrazol‐1‐ylmethyl]pyridine), which has a rhombic core structure abbreviated as {FeIII2FeII2}. Magnetic susceptibility measurements and single‐crystal X‐ray diffraction analyses revealed that 1 underwent thermally‐induced spin transition with the thermal hysteresis. The FeII site in 1 behaved as a spin crossover (SCO) unit, and significant deformation of its octahedron was observed during the spin transition process. Moreover, the distortion of the FeII centers actuated anisotropic deformation of the rhombic {FeIII2FeII2} core, which was spread over the whole crystal through the subsequent molecular rearrangements, leading to the colossal anisotropic thermal expansion. Our results provide a rational strategy for realizing the colossal anisotropic thermal expansion and shape memory effects by tuning the magnetic bistability. [ABSTRACT FROM AUTHOR]

C16H20N4Ni, monoclinic, P21/n (no. 14), a = 7.6578(10) Å, b = 17.184(2) Å, c = 11.6581(15) Å, β = 100.837(2)°, V = 1506.7(3) Å3, Z = 4, Rgt(F) = 0.0356, wRref(F2) = 0.0945, T = 296(2) K.

C17H21N3O5, monoclinic, P21/n (no. 14), a = 9.2278(16) Å, b = 15.093(3) Å, c = 12.698(2) Å, β = 105.195(12)°, V = 1706.7(5) Å3, Z = 4, Rgt(F) = 0.0553, wRref(F2) = 0.1662, T = 296 K.

C16H20N4Ni, monoclinic, P21/n (no. 14), a = 7.6578(10) Å, b = 17.184(2) Å, c = 11.6581(15) Å, β = 100.837(2)°, V = 1506.7(3) Å3, Z = 4, Rgt(F) = 0.0356, wRref(F2) = 0.0945, T = 296(2) K. [ABSTRACT FROM AUTHOR]

The design of magnetic molecular materials exhibiting multiple functions has garnered significant interest owing to their potential applications in molecular switches, sensors, and data storage devices. In this study, we synthesized a two-dimensional (2D) Fe II -based Hofmann-type coordination polymer, namely {Fe(DPPE) 2 [Ag(CN) 2 ] 2 }·2EtOH (1), using a luminescent ligand 1,1-diphenyl-2,2-di(4-pyridylbiphenyl)ethylene (DPPE). Single-crystal structural analyses and magnetic measurements revealed a thermally induced spin crossover (SCO) with the transition temperature T 1/2 = 231 K. Variable-temperature fluorescence emission spectra indicated the coexistence of spin crossover and fluorescence properties. Moreover, a pronounced dielectric change (Δ ε ' = 1.2 at 0.5 kHz) was observed during the SCO process, confirming the simultaneous magnetic and dielectric switching arising from the rearrangement of 3 d electrons and deformation of the Fe II -centered coordination sphere. This work provides an approach to explore the interplay between magnetic, dielectric, and fluorescence properties, and holds significance for developing multifunctional molecular materials.

Cyano-bridged 4d-4f molecular nanomagnets have re-called increasing research interests in molecular magnetism since they offer more possibilities in achieving novel nanomagnets with versatile structures and magnetic interactions. In this work, four β-diketone ligands bearing different substitution N-sites were designed and synthesized, namely 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL 1 ), 1,3-Bis (3-pyridyl)-1,3-propanedione (HL 2 ), 1-(4-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL 3 ), and 1,3-Bis (4-pyridyl)-1,3-propanedione (HL 4 ), to tune the magnetic relaxation behaviors of cyano-bridged {Dy III Mo V } systems. By reacting with DyCl 3  ⋅ 6H 2 O and K 4 Mo(CN) 8  ⋅ 2H 2 O, four cyano-bridged complexes, namely {[Dy[Mo V (CN) 8 ](HL 1 ) 2 (H 2 O) 3 ]} ⋅ 6H 2 O (1), {[Dy[Mo V (CN) 8 ](HL 2 )(H 2 O) 3 (CH 3 OH)]} 2  ⋅ 2CH 3 OH ⋅ 3H 2 O (2), {[Dy[Mo V (CN) 8 ](HL 3 )(H 2 O) 2 (CH 3 OH)] ⋅ H 2 O} n (3), and {[Dy[Mo V (CN) 8 ](HL 4 ) 2 (H 2 O) 3 ]} ⋅ 2H 2 O⋅CH 3 OH (4) were obtained. Structural analyses revealed that 1 and 4 are binuclear complexes, 2 has a tetragonal structure, and 3 exhibits a stair-like polymer chain structure. The Dy III ions in all complexes have eight-coordinated configurations with the coordination spheres DyO 7 N 1 for 1 and 4, DyO 6 N 2 for 2, and DyO 5 N 3 for 3. Magnetic measurements indicate that 1 is a zero-field single-molecule magnet (SMM) and complexes 2-4 are field-induced SMMs, with complex 4 featuring a two-step relaxation process. The magnetic characterizations and ab initio calculations revealed that changing the N-sites in the β-diketone ligands can effectively alter the structures and magnetic properties of cyano-bridged 4d-4f nanomagnets by adjusting the coordination environments of the Dy III centers., (© 2023 Wiley-VCH Verlag GmbH.)

Colossal and anisotropic thermal expansion is a key function for microscale or nanoscale actuators in material science. Herein, we present a hexanuclear compound of [(Tp*)Fe III (CN) 3 ] 4 [Fe II (Ppmp)] 2 ⋅2 CH 3 OH (1, Tp*=hydrotris(3,5-dimethyl-pyrazol-1-yl)borate and Ppmp=2-[3-(2'-pyridyl)pyrazol-1-ylmethyl]pyridine), which has a rhombic core structure abbreviated as {Fe III 2 Fe II 2 }. Magnetic susceptibility measurements and single-crystal X-ray diffraction analyses revealed that 1 underwent thermally-induced spin transition with the thermal hysteresis. The Fe II site in 1 behaved as a spin crossover (SCO) unit, and significant deformation of its octahedron was observed during the spin transition process. Moreover, the distortion of the Fe II centers actuated anisotropic deformation of the rhombic {Fe III 2 Fe II 2 } core, which was spread over the whole crystal through the subsequent molecular rearrangements, leading to the colossal anisotropic thermal expansion. Our results provide a rational strategy for realizing the colossal anisotropic thermal expansion and shape memory effects by tuning the magnetic bistability., (© 2023 Wiley-VCH GmbH.)