Same Not the Same: Thermally Driven Transformation of Nickel Phosphinate-Bipyridine One-Dimensional Chains into Three-Dimensional Coordination Polymers

Abstract

Three 1D nickel coordination polymers (CPs) based on P,P'-diphenylethylenediphosphinic acid and three different bis-pyridine co-ligands, namely 4,4'-bipyridine (bipy), 1,2-bis(4-pyridyl)ethane (bpyane) and 1,2-bis(4-pyridyl)ethane (bpy-ene), were prepared in mild hydrothermal conditions from water solutions containing the dissolved reagents. The CPs have formula [Ni(H2O)4(bipy)•pc2p]n (1),[Ni(H2O)4(bpy-ane)•pc2p]n (2), and [Ni(H2O)4(bpy-ene)•pc2p]n (3) and their structures were characterized by single crystal X-ray diffraction. They are constituted of infinite Ni(H2O)4(bis-pyridine) 1D rows connected, through hydrogen bonds, with the phosphinic acids placed among adjacent rows. Although the formulas and the structural topologies of the three compounds are almost identical, they behave in different manners upon heating. Compound 1 yields an amorphous phase when water molecules are thermally removed, whereas compound 3 undergoes interesting phase transformations derived from the connection of Ni atoms with the phosphinates oxygen atoms, increasing the dimensionality to 3D and maintaining crystallinity. The behavior of compound 2 has some analogies to that of 3 although a complete structural characterization was not performed because of a significant crystallinity loss of the heated phase. The structural features were studied by means of combination of variable temperature (VT) single crystal and powder X-ray diffraction and thermogravimetric analysis.

Platonic Relationships in Metal Phosphonate Chemistry: Ionic Metal Phosphonates

“…There is a complex network of hydrogen bonds that involve the Ni-coordinated waters, the lattice water molecules, and the -PO3H − moieties. The structure of Ni-bpy-EDPA is reminiscent of that in the 1D nickel coordination polymer based on P,P'-diphenylethylenediphosphinic acid and 4,4'-bipyridine [21]. The structure of Ni-bpy-EDPA is different from the ones of other salts described thus far, in that the cationic portion of the salt is a cationic coordination polymer, composed of a cationic trans-[Ni(H 2 O) 4 (4,4'-bpy)] 2+ unit, propagating along the ab plane (Figure 6a,c).…”

“…There is a complex network of hydrogen bonds that involve the Ni-coordinated waters, the lattice water molecules, and the -PO 3 H − moieties. The structure of Ni-bpy-EDPA is reminiscent of that in the 1D nickel coordination polymer based on P,P'-diphenylethylenediphosphinic acid and 4,4'-bipyridine [21].…”

“…Three 1D nickel coordination polymers based on P,P'-diphenylethylenediphosphinic acid and three different bis-pyridine co-ligands, namely 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethane and 1,2-bis(4-pyridyl)ethane, were prepared in mild hydrothermal conditions. They all contained 1D "Ni-bipyridyl" chains, with the phosphinate playing the role of the counterion [21]. The synthesis and crystal structure of Mg(2-AEPH) 2 ·8H 2 O (2-AEPH = 2-aminoethylphosphonate) were reported [22].…”

Mechanochemical Access to Elusive Metal Diphosphinate Coordination Polymer

“…The isolation of two isoreticular metal organic nano tubes (MONT) built by using copper(II) metal ion, pcp and two types of bi-pyridine was one of our most interesting results [24,25], also due to the different behavior of the two materials in water. [21] On the other hand, pc 2 p and pxylp ligands were found to form 2D and 3D coordination polymers easily [26][27][28]. One of the latter, features porous channels able to reversibly adsorb methanol [26].…”

“…One of the latter, features porous channels able to reversibly adsorb methanol [26]. Under heating, different pseudo polymorph coordination polymers have been obtained upon removal of the coordinated water molecules [26][27][28].…”