Crystal exploring, Hirshfeld surface analysis, and properties of 4′‐(furan‐2‐yl)‐2,2′:6′,2″‐terpyridine complexes of nickel (II): New precursors for the synthesis of nanoparticles

Abstract

A series of mono‐ and bis‐terpyridine complexes of nickel (II) based on the 4′‐(furan‐2‐yl)‐2,2′:6′,2″‐terpyridine (ftpy) have been synthesized and structurally characterized using elemental analysis, infrared spectroscopy, and single crystal X‐ray diffraction. The reaction of NiCl2•6H2O with ftpy has been resulted in the formation of new bis‐terpyridine complex [Ni (ftpy)2](PF6)•2H2O (1). The new complex [Ni (ftpy)2](PF6)2 (2), obtained during the crystallization of 1 in methanol, was characterized using X‐ray crystallography, which shows that six nitrogen atoms from terpyridine ligands occupy the coordination sites around the Ni (II) in a distorted octahedral geometry. On the other hand, the reaction of NiCl2•6H2O with ftpy in a 1:2 or 1:1 mole ratio in methanol in the presence of KSCN affords two new thiocyanato complexes [Ni (ftpy)2](SCN)2•2H2O (3) and [Ni (ftpy)(NCS)2(H2O)]•2H2O (4), respectively. The crystal structure of 3 reveals that nickel (II) is hexa‐coordinated in a distorted octahedral geometry NiN6 involving six atoms of two ftpy ligand; the ftpy ligands are perpendicular to each other. The new complex [Ni (ftpy)(NCS)2(DMSO)]•DMSO (5) is obtained during the crystallization of 4 in DMSO. The crystal structure of 5 reveals that the nickel (II) is hexa‐coordinated by three nitrogen atoms of ftpy, two NCS−, a DMSO in a slightly distorted octahedral geometry. The X–H (XH, C, N, O) bond interactions control the arrangement of the supramolecular 3D framework. Hirshfeld surface analyses and two‐dimensional fingerprint plot reveal that the main interactions are H–H contacts for 2, 3, and 5, which comprise 34.1%, 37.2%, and 34.6%, respectively. Thermal decomposition of the coordination complexes led to the formation of Ni, NiO, and Ni2P2O7 nanoparticles (NPs). The resulting NPs were fully characterized by powder XRD, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), and energy‐dispersive X‐ray spectroscopy (EDX). The formation of these NPs indicates the role of the precursor complexes and counterion. Our results indicate that the NPs with the smaller size could be obtained at calcination temperature of 600 °C. Thermal and luminescent properties of complexes have been discussed in detail.

Ni(2,2′:6′,2′′-terpyridine)2: a high-spin octahedral formal Ni(0) complex

“…The average Ni–N bond lengths of 2.127(7) [outer] and 1.985(4) [inner] Å slightly differ from the ones found for Ni II (tpy) 2 Cl 2 (2.02–2.14) Å, 16 and are similar those found for dicationic [Ni(ftpy) 2 ] 2+ (ftpy = 4′-(furan-2-yl)-tpy) of 2.107(8) [outer] and 1.991(5) [inner] Å. 17 More telling, however, are the average C–C bond lengths between pyridine rings, which is 1.456(12) Å for our structure and 1.493(12) Å for [Ni(ftpy) 2 ] 2+ , 17 the latter which is consistent with that of free tpy at 100 K. 18 This trend is seen in the Fe system in which the average C–C bond lengths between pyridine rings shorten in going from [Fe(tpy) 2 ] 2+ to [Fe(tpy) 2 ] 0 , 1.467(4) to 1.452(4) Å, which Wieghardt attributes to reduction of the ligands. 19 Moreover, Ni 0 (bpy) 2 shows shorter Ni–N distances, around 1.92 Å, 14 and Ni I (tpy)R (R = Br, Me) range between 1.92–2.04.…”

“…However, this species only represents 1% of the total sample which suggests that the major species has S = 1 or 2. Following the Evans method, which uses difference in the NMR chemical shift in a solvent caused by the presence of a paramagnetic species, 17 we measured the effective magnetic moment ( μ eff ) in the solution of complex 1 , obtaining a value of 4.9(2) μ B in THF and 5.2(2) μ B in toluene. These results are consistent with a S = 2 ground-state for 1 in solution.…”