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A mononuclear cobalt(ii) complex [C 5 H 8 N 3 ] 2 [CoCl 4 (C 5 H 7 N 3 ) 2 ] (I) was synthesized and structurally characterized. Single crystal X-ray diffraction analysis indicates that monometallic Co(ii) ions acted as coordination nodes in a distorted octahedral geometry, giving rise to a supramolecular architecture. The latter is made up of a ½ unit form composed of an anionic element [Co 0.5 Cl 2 (C 5 H 7 N 3 )] - and one 2-amino-4-methylpyrimidinium cation [C 5 H 8 N 3 ] + . The crystalline arrangement of this compound adopts the sandwich form where inorganic parts are sandwiched between the organic sheets following the [100] direction. More information regarding the structure hierarchy has been supplied based on Hirshfeld surface analysis; the X⋯H (X = N, Cl) interactions play a crucial role in stabilizing the self-assembly process of I, complemented by the intervention of π⋯π electrostatic interaction created between organic entities. Thermal analyses were carried out to study the thermal behavior process. Static magnetic measurements and ab initio calculations of compound I revealed the easy-axis anisotropy character of the central Co(ii) ion. Two-channel field-induced slow-magnetic relaxation was observed; the high-frequency channel is characterized by underbarrier relaxation with U eff = 16.5 cm -1 , and the low-frequency channel involves a direct relaxation process affected by the phonon-bottleneck effect., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Two new complexes, bis-[4-amino-3,5-bis-(pyridin-2-yl)-1,2,4-triazole-κ 2 N 2 , N 6 ]bis-(dicyanamide-κ N 8 )copper(II), [Cu(abpt) 2 (dca) 2 ] (1) and bis-[4-amino-3,5-bis-(pyridin-2-yl)-1,2,4-triazole-κ 2 N 2 , N 6 ]bis-(dicyanamide-κ N 8 )cobalt(II), [Co(abpt) 2 (dca) 2 ] (2), have been prepared and magneto-structurally characterised. Single crystal studies of both complexes have shown that their crystal structures are molecular, in which the central atoms are six-coordinated in the form of a distorted octahedron by two bidentate abpt and two monodentate dca ligands. Even if both complexes have the same composition and crystallize in the same P 1̄ space group, they are not isostructural. Both structures contain strong intermolecular N-H⋯N hydrogen bonds and π-π stacking interactions. IR spectra are consistent with the solved structures of both complexes and confirmed the terminal character of the dca ligands and the bidentate coordination of the abpt ligands. The analysis of the magnetic properties showed that both complexes exhibit field-induced slow spin-phonon relaxation. In both complexes, the slow spin-phonon relaxation is influenced by a severe phonon-bottleneck effect that affects the direct process, a dominant relaxation mechanism at low temperatures in both complexes. The phonon-bottleneck effect in 1 was suppressed by simply reducing the crystallite size, and further analysis of the field dependence of the relaxation time yielded the characteristic energy of vibrational modes of 11 cm -1 participating in the Raman process at low magnetic fields. The analysis of magnetic properties and ab initio calculations confirmed that 2 represents a system with a moderate uniaxial anisotropy yielding an average energy barrier of 82 cm -1 (from all four nonequivalent Co(II) sites in the structure of 2).

Detailed structural information is essential for understanding the properties of TCNQ and TCNQF 4 compounds (TCNQ = 7,7,8,8-tetracyanoquinodimethane; TCNQF 4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane). The ineludible requirement of obtaining crystals of a size and quality sufficient to yield a successful X-ray diffraction analysis has been challenging to satisfy because of the instability of many of these compounds in solution. Crystals of two new complexes of TCNQ, [ trans -M(2 ampy ) 2 (TCNQ) 2 ] [M = Ni ( 1 ), Zn ( 2 ); 2ampy = 2-aminomethylpyridine], as well as unstable [Li 2 (TCNQF 4 )(CH 3 CN) 4 ]·CH 3 CN ( 3 ), can be prepared in minutes by a horizontal diffusion technique and can be harvested easily for X-ray structural studies. Compound 3 , previously described as "Li 2 TCNQF 4 ," forms a one-dimensional (1D) ribbon. Compounds 1 and 2 can also be obtained as microcrystalline solids from methanolic solutions of MCl 2 /LiTCNQ/2 ampy . Their variable-temperature magnetic studies confirmed a contribution of strongly antiferromagnetically coupled pairs of TCNQ •- anion radicals at higher temperatures with exchange coupling J / k B = -1206 K and J / k B = -1369 K for 1 and 2 , respectively, estimated using a spin dimer model. The presence of magnetically active anisotropic Ni(II) atoms with S = 1 in 1 was confirmed, and the magnetic behavior of 1 , representing an infinite chain of alternating S = 1 sites and S = 1/2 dimers, was described by a spin-ring model suggesting ferromagnetic exchange coupling between Ni(II) sites and anion radicals., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)