Conjugation of a Silver-Based Coordination Polymer with Curcumin: A New Case of an Inorganic Polymeric Co-crystal

Abstract

A new structural form of the already reported silverbased 1D coordination polymer (CP) [(bpy)Ag (OTf)] ∞ (bpy = 2,2′-bipyridine; OTf = trifluoromethanesulfonate) has been synthesized and fully characterized through single-crystal and powder XRD, DSC, and FTIR analysis. The reaction of both structural forms of the Ag(I) CP with curcumin (curc) afforded the formation of a new solid form, specifically an inorganic polymeric co-crystal between curc and [(bpy)Ag (OTf)] in a 1: 4 molar ratio, respectively. The co-crystal has been characterized both in solution and in the solid state through 1 H NMR, PXRD, DSC, IR, and UV−vis spectroscopies. In addition, a thorough computational study has been carried out to reveal the possible interaction modes between the co-crystal components. The Ag(I) compounds here presented have been preliminarily tested for antimicrobial activity against Staphylococcus aureus and Escherichia coli strains, all showing promising results.

Hybrid Ethylcellulose Polymeric Films: Ag(I)‐Based Components and Curcumin as Reinforcing Ingredients for Enhanced Food Packaging Properties

“…In particular, the curc-EC sample is characterized by the absence of the curc melting transition (see ref. [25] for the DSC curves of the additives), indicating a good miscibility between the polymer and the polyphenol, as already revealed by PXRD analysis. Moreover, within the DSC trace of curc-EC, the T g occurs at a temperature five degrees lower than that of EC-0, pointing out a slight plasticizing effect exerted by curc on EC matrix.…”

“…[25] The same applies when these Ag(I) polymers are mixed with EC powder in the solid state. [25] On this basis, the presence of the EC polymer in the dichloromethane solution seems be responsible for the transformation of the Ag(I) polymers into a discrete compound. Being the Ag α À EC and Ag β À EC undistinguishable, hereafter they will be referred to as AgÀ EC.…”

“…The recently reported Ag(I) coordination polymer, in both its structural forms (α-[(bpy)Ag(OTf)] ∞ and β-{[(bpy)Ag][OTf]} ∞ ), and the [(bpy)Ag(OTf)] ∞ -curc polymeric co-crystal have been selected as active ingredients for the preparation of EC composite films (named Ag α À EC, Ag β À EC, cocrystÀ EC, respectively) on the basis of the good performances shown in preliminary antibacterial test. [25] Unloaded EC films (EC-0) and films embedding curc as an unique additional component (curc-EC) were also prepared as control samples.…”

“…However, these reflections do not correspond to either the α-or the β-form of the Ag(I) coordination polymer (Figure 1b, blue and pink line, respectively). Considering the structural isomerism characterizing Ag(I) coordination polymers incorporating 2,2'-bipyridine (bpy) as a ligand and trifluoromethanesulfonate (OTf) as a counterion, [25,33,34] the re-crystallization of the Ag(I) polymers within the EC matrix into another form could have occurred. From an accurate comparison between the diffractogram of AgÀ EC (α-and β-interchangeably) and the simulated PXRD patterns derived from the single-crystal X-ray structures of the ionic complex [(bpy) 2 Ag]OTf, reported in the Cambridge Crystallographic Data Centre (CCDC), [35] the identification of the new specie has been achieved (Figure 1c).…”

“…Fourier Transform Infrared analysis was carried out on the film samples in the mid-infrared area (4000-450 cm À 1 ) with a PerkinElmer Spectrum 100 FT-IR spectrometer. KBr pellets were prepared only to acquire the spectra of the additives in their powder form.α-[(bpy)Ag(OTf)] ∞ , β-{[(bpy)Ag][OTf]} ∞ , and [(bpy)Ag-(OTf)] ∞ -curc (bpy = 2,2'-bipyridine; OTf = trifluoromethanesulfonate) were synthetized according to the procedures reported, [25] and all the characterizations are consistent with those previously reported.…”