Temperature‐Dependent Guest‐Driven Single‐Crystal‐to‐Single‐Crystal Ligand Exchange in a Two‐Fold Interpenetrated Cd^II Grid Network

Abstract

A doubly interpenetrated square-grid coordination polymer {[Cd(ImBNN)(2)(CF(3)SO(3))(2)])guest}(n) (1) (guest = C(7)H(8) and ImBNN = 2,5-bis[4'-(imidazol-1-yl)phenyl]-3,4-diaza-2,4-hexadiene) that contains cavities able to accommodate toluene guest molecules has been assembled by the reaction of the Schiff base ligand ImBNN and Cd(CF(3)SO(3))(2). The framework 1 shows dynamism in either temperature-dependent expansion and shrinkage or cooperatively temperature-dependent guest-driven ligand exchange at the metal center. Studies of guest removal/uptake by heating in a vacuum, cooling in air, and then heating in toluene at reflux have revealed a series of single-crystal-to-single-crystal structural transformations: complex 1 lost toluene guests and captured water molecules to give guest-free 1 b via a proposed metastable phase 1 a, and 1 b could readsorb toluene guests to give 1', which represents a restored 1. These structural changes establish an indirect recoverable process that involves ligand exchange in the coordination sphere and guest exchange in the cavity accompanied by the cleavage/formation of Cd-O bonds and CF(3)SO(3)(-) anion-shifting. In contrast, direct heating of 1 in the absence of a vacuum resulted in thermostable 1 c, confirmed by X-ray powder diffraction as a new phase that could not be converted back into 1 and that had lost the ability of readsorbing toluene guests.

How 2-periodic coordination networks are interweaved: entanglement isomerism and polymorphism

“…with sql-type networks. 60,61 The long bent geometry of bridging ImBNN ligands predetermines the undulated geometry of layers that leads to interpenetration. However, the intercalation of aromatic molecules reduces the degree of interpenetration from three to two without altering the network topology and catenation mode of rings.…”

Recent advance in porous coordination polymers from the viewpoint of crystalline-state transformation

“…[87] Temperature-dependent guest-driven single-crystal-to-single-crystal ligand exchange in a two-fold interpenetrated Cd II grid network. [127] BAI JunFeng Nanjing University Topology diversity and reversible crystal-to-amorphous transformation properties of 3D cobalt coordination polymers from a series of 1D rodlike dipyridyl-containing building blocks and a flexible tripodal acid with additional amide groups. [128] Synthesis, structure, water-induced reversible crystal-to-amorphous transformation, and luminescence properties of novel cationic spacer-filled 3D transition metal supramolecular frameworks from N,N',N''-tris(carboxymethyl)-1,3,5-benzenetricarboxamide.…”

Neutral N-donor ligand based flexible metal–organic frameworks

“…Su et al extended this concept through fabrication of a Cd(II) based MOF [(Cd(ImBNN) 2 (CF 3 SO 3 ) 2 ).guest] n , (ImBNN -2,5bis[4'-(imidazol-1-yl)phenyl]-3,4-diaza-2,4-hexadiene) bearing weakly coordinated triflate anions and free toluene molecules. 52 Upon removal of the toluene molecules by Please do not adjust margins Please do not adjust margins heating, the metal-anion bond is weakened. When the compound was cooled under atmospheric conditions, one water molecule replaced the triflate anion leading to slight structural changes.…”