To investigate the influence of the coordination geometry on the magnetization relaxation dynamics, two geometric isomers of a fivecoordinate low-spin Co(II) complex with the general molecular formula [Co(DPPE) 2 Cl]SnCl 3 (DPPE = diphenylphosphinoethane) were synthesized and structurally characterized. While one isomer has a square pyramidal geometry (Co-SP (1)), the other isomer figures a trigonal bipyramidal geometry (Co-TBP (2)). Both complexes were already reported elsewhere. The spin state of these complexes is unambiguously determined by detailed direct current (dc) magnetic data, X-band, and high-frequency EPR measurements. Slow relaxation of magnetization is commonly observed for systems with S > 1/2. However, both 1 and 2 show field-induced slow relaxation of magnetization. Especially 1 shows relaxation times up to τ = 35 ms at T = 1.8 K, which is much longer than the reported values for undiluted Co(II) low-spin monomers. In 2, the maximal field-induced relaxation time is suppressed to τ = 5 ms. We attribute this to the change in g-anisotropy, which is, in turn, correlated to the spatial arrangement of ligands (i.e., coordination geometry) around the Co(II) ions. Besides the detailed electronic structure of these complexes, the experimental observations are further corroborated by theoretical calculations.
Developing robust, wearable, and biocompatible energy harvesting devices with bulk oxides (ceramics and perovskites) is extremely hard to achieve due to their zero mechanical flexibility, heavy metal toxicity, and tunability of properties. Alternatively, discrete inorganic complexes can be an excellent choice to overcome the above‐stated issues, thanks to appropriate molecular engineering. Herein, we report an above‐room‐temperature ferroelectric discrete molecular complex [Cu(L‐phe)(bpy)(H2O)]PF6⋅H2O (1) which is suitable for piezoelectric energy harvesting due to its large values of piezoelectric co‐efficient (d33=10 pm V−1) and spontaneous polarization (Ps=1.3 μC cm−2). Among the devices prepared with the composite films of polyvinyl alcohol (PVA) and various weight % composition of 1, the 10 Wt % composite shows the highest output voltage of 8 V, a power density of 0.85 μW cm−2, and output current of 5 μA, which is highest for any discrete inorganic complex reported to date.
Developing robust, wearable, and biocompatible energy harvesting devices with bulk oxides (ceramics and perovskites) is extremely hard to achieve due to their zero mechanical flexibility, heavy metal toxicity, and tunability of properties. Alternatively, discrete inorganic complexes can be an excellent choice to overcome the above‐stated issues, thanks to appropriate molecular engineering. Herein, we report an above‐room‐temperature ferroelectric discrete molecular complex [Cu(L‐phe)(bpy)(H2O)]PF6⋅H2O (1) which is suitable for piezoelectric energy harvesting due to its large values of piezoelectric co‐efficient (d33=10 pm V−1) and spontaneous polarization (Ps=1.3 μC cm−2). Among the devices prepared with the composite films of polyvinyl alcohol (PVA) and various weight % composition of 1, the 10 Wt % composite shows the highest output voltage of 8 V, a power density of 0.85 μW cm−2, and output current of 5 μA, which is highest for any discrete inorganic complex reported to date.
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