Selective gelation of N-(4-pyridyl)nicotinamide by copper(ii) salts

Abstract

ARTICLE This journal isWe report the selective gelation properties of copper(II) complexes of N-(4pyridyl)nicotinamide (4PNA). The morphology of the xerogels was examined by scanning electron microscopy (SEM). Correlation of X-ray powder diffraction (XRPD) pattern of the xerogels and single crystal structure of copper(II) acetate complex suggests that the single crystal X-ray data represents a good structural model for the gel fibers themselves and that gelation arises from the presence of a 1D hydrogen bonded chain between gelator amide groups and coordinated anions, while the presence of strongly bound water in non-gelator systems results in the formation of more extensively hydrogen bonded crystalline networks. The selective gelation of all the copper(II) salts compared to the other metal salts may be attributed to Jahn-Teller distorted nature of copper(II), which weakens water binding in all copper(II) salts.

Role of N–Oxide Moieties in Tuning Supramolecular Gel-State Properties

“…We have been successful in identifying the role of various nonbonding interactions in gel formation by comparing the molecular assembly in crystalline and gel/dried gel states [ 30 , 43 , 44 , 45 ]. Although, the xerogel does not represent the exact structure of the gel state since the drying process can lead to a morphological change or phase transition [ 46 ], this approach is still recognized as the most useful strategy to unravel the self-assembly of a gelator [ 3 , 7 , 29 , 30 , 43 , 44 , 45 ]. The self-assembly of L 1 and L 2 in the gel state was correlated with respective crystal structures by comparing the powder X-ray pattern of the bulk crystals and dried gels with the crystal structure.…”

“…The amide/urea functionalized LMWGs can be considered as classical stimuli-responsive soft materials due to their response to an external stimulus such as light, redox, pH, and salts/ions [ 29 , 37 , 43 , 47 ]. We have shown that the anion responsive properties of supramolecular gels can be used to detect cyanide anions in water by monitoring the gel to sol transition [ 44 ].…”

Stimuli responsive dynamic transformations in supramolecular gels

“…394 In some cases, aging can causes a considerable weakening of interlocked fibre networks leading to spontaneous evolution to crystallization. [395][396][397][398][399][400][401] Furthermore, there are examples where the aged gel shows a shrinking behavior. [402][403][404] Recently, Sugiura et al constructed a hydrogel system involving hydrazone-oxime exchange reaction in response to hydroxylamine (Fig.…”

Computational Tools to Rationalize and Predict the Self-Assembly Behavior of Supramolecular Gels

“…Both supramolecular gelation and crystallization are non-equilibrium self-assembly processes that occur under supersaturated conditions and are characterized by a nucleation and growth phase [ 102 , 103 ]. For this reason, many experimental studies on supramolecular gels report powder X-ray diffraction data of the dried xerogel with the aim of extracting useful information on the structure of the gel network [ 5 , 104 , 105 ]. From the 1960s onwards, crystal structure prediction (CSP) has become a field on its own and has experienced an enormous development of applicable techniques able to predict the crystal morphology based on the molecular structure [ 106 , 107 , 108 , 109 , 110 ].…”