Rich Pseudopolymorphic Behavior of the Tetranuclear [Ni₄(dpyatriz)₂(NO₃)₈] Complex

Abstract

Reaction of nickel(II) nitrate with the dpyatriz ligand, namely 2,4,6-tris(bis(pyridin-2-yl)amino)-1,3,5-triazine, in acetonitrile produces a tetranuclear NiII coordination compound, [Ni4(dpyatriz)2(NO3)8(CH3CN)2(H2O)2].2CH3CN (1), the crystal structure of which has been determined by X-ray diffraction using a synchrotron source. 1 has been characterized by IR and UV-vis spectroscopy, elemental and thermogravimetric analyses, and magnetic susceptibility measurements. Its solid-state structure exhibits remarkable anion...pi interactions between coordinated nitrate ions and the triazine rings. In addition, a thorough X-ray powder diffraction study has revealed a number of pseudopolymorphic phases (2-5), resulting from various degrees of hydration/solvation of the [Ni4(dpyatriz)2] core. The interconversion scheme among the different phases has been determined using controlled heating, and the basic structural features of the different pseudopolymorphs have been assessed through ab initio powder diffraction methods.

Polymorphic Coordination Networks Responsive to CO2, Moisture, and Thermal Stimuli: Porous Cobalt(II) and Zinc(II) Fluoropyrimidinolates

“…Finally, we should highlight that, in the absence of suitable single crystals, all the valuable structural information presented on the title PCPs have been retrieved by applying ab initio XRPD structure solution methods, sagaciously coupled to thermal XRPD investigations. [34] Experimental Section…”

Metalorganic frameworks based on the 1,4-bis(5-tetrazolyl) benzene ligand: The Ag and Cu derivatives

“…Only at a later stage, we increased the complexity of the polytopic N-ligands, aiming at the formation of oligomeric and polymeric species with different functional properties. For example, using substituted triazines [4], bisimidazolates [5] and other substituted heterocycles [6], we have isolated and fully characterised several highly functional materials, such as catalytically active species (soluble oligomers [7] and insoluble 3D polymers [8]) or extended solids capable of molecular sensing and recognition [3,9]. Since many of these materials do not afford single crystals of suitable quality, we attained their full structural characterisation resorting to state-ofthe-art powder diffraction methods, occasionally coupled to thermodiffractometry [10] and 13 C CP-MAS NMR spectroscopy [11].…”

Proficiency of the electron-deficient 1,3,5-triazine ring to generate anion–π and lone pair–π interactions

“…The contact distance O41-N1 is significantly below the corresponding sum of van der Waals radii (namely 3.07 A ˚), 7 and the contact distances O41-C2 and O41-C6 are close to the sum of the van der Waals radii (O + C), which amounts to 3.22 A ˚.7 The resulting interaction can therefore be considered as weaker than that found in 1 (see above), as deduced from the O41-triazine centroid distance of 3.345(2) A ˚, which is above the minimum value of 3.03 A ˚defining a strong bonding interaction between an oxygen atom (from a nitrate ion for instance) and a 1,3,5-triazine ring. 7,35,36 Actually, this weaker bonding contact (compared to the bromide-triazine contact observed for 1) could also be related to the fact that the nitrate ion is involved in an additional anion-p interaction, through a second oxygen atom (i.e. O42), with the triazine ring from an adjacent coordination molecule (Fig.…”