New Bis-Pyrazole-Bis-Acetate Based Coordination Complexes: Influence of Counter-Anions and Metal Ions on the Supramolecular Structures

Abstract

A new flexible bis-pyrazol-bis-acetate ligand, diethyl 2,2’-(pyridine-2,6-diylbis (5-methyl-1H-pyrazole-3,1-diyl))diacetate (L), has been synthesised, and three coordination complexes, namely, [Zn(L)2](BF4)2 (1), [MnLCl2] (2) and [CdLCl2] (3) have been obtained. All ligands and complexes were characterised by IR, mass spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. Single crystal X-ray diffraction experiment revealed that the primary supramolecular building block of 1 is a hexagonal chair shaped 0D hydrogen bonded synthon (stabilised by C–H∙∙∙O hydrogen bonding and C=O∙∙∙π interactions), which further built into a 2D corrugated sheet-like architecture having a 3-c net honeycomb topology, and finally extended to a 3D hydrogen bonded network structure having a five nodal 1,3,3,3,7-c net, through C–H∙∙∙F interactions. On the other hand, the two crystallographically independent molecules of 2 exhibited two distinct supramolecular structures such as 2D hydrogen bonded sheet structure and 1D zigzag hydrogen bonded chain, sustained by C–H∙O and C–H∙∙∙Cl interactions, which are further self-assembled into a 3,4-c network structure, and 3 showed a 2D hydrogen bonded sheet structure. The supramolecular structural diversity in these complexes is due to the different conformations adopted by the ligands, which are mainly induced by different metal ions with coordination environments controlled by different anions. Hirshfeld surface analysis was explored for the qualitative and quantitative analysis of the supramolecular interactions.

Synthesis and cytotoxicity against tumor cells of pincer N-heterocyclic ligands and their transition metal complexes

“… 15 The synthesis protocol and characterization of L′, 1′ and 2′ have been described in our previous work. 30 …”

“…15 The synthesis protocol and characterization of L 0 , 1 0 and 2 0 have been described in our previous work. 30 2.2.1 Synthesis of diethyl 1,1 0 -(pyridine-2,6-diyl) bis(5methyl-1H-pyrazole-3-carboxylate) (L). The synthesis of L was carried out adapting a literature method.…”

“…28,29 To this end, we have designed novel derivatives of nitrogenchelating pyrazolyl-pyridine ligands with CC (L 0 ) and CN (L) junctions, to study their in vitro individual anticancer activities with particular emphasis on their complexes of Co, Fe, Ni, and Mn. This led us to prepare diethyl 2,2 0 -(pyridine-2,6-diylbis(5methyl-1H-pyrazole-3,1-diyl)) diacetate (L 0 ) 30…”

“…To this end, we have designed novel derivatives of nitrogen-chelating pyrazolyl–pyridine ligands with CC (L′) and CN (L) junctions, to study their in vitro individual anticancer activities with particular emphasis on their complexes of Co, Fe, Ni, and Mn. This led us to prepare diethyl 2,2′-(pyridine-2,6-diylbis(5-methyl-1 H -pyrazole-3,1-diyl)) diacetate (L′) 30 and diethyl 1,1′-(pyridine-2,6-diyl) bis(5-methyl-1 H -pyrazole-3-carboxylate) (L) ( Scheme 1 ). Metal complexes [CoL 2 ](ClO 4 ) 2 (1), [FeL 2 ](ClO 4 ) 2 (2), [NiL 2 ](ClO 4 ) 2 (3), [MnLCl 2 ] (4), [MnL′Cl 2 ] (1′) and [CdL′Cl 2 ] (2′) were also investigated.…”

Novel family of bis-pyrazole coordination complexes as potent antibacterial and antifungal agents

“…Such five-membered heterocyclic ligands associated with hydrogen bonding as well as π–π interactions can lead to interesting features, such as flexibility, ductility and chelation properties for the resulting coordination complexes. 11 The construction of these complexes depends on the effect of hydrogen bonding, 12 donor atoms, 13 counter anions, 14 solvent 15 and the topologies of the selected ligand. 16 In addition, such organic molecules were found to exhibit various properties, be pharmacological, 17 chemosensory and photophysical, 18 optical and morphological properties, 19 to name but a few.…”