Chain Length and Thermal Sensitivity of the Infrared Spectra of a Homologous Series of Anhydrous Silver(I)n-Alkanoates

Abstract

The thermal and chain length sensitivity of the infrared spectra of some solid state anhydrous silver(I) salts (n-octanoate to n-eicosanoate, inclusive) are discussed. At ambient temperature, the tilted alkyl chains, anchored to the metal planes via chelating bidentate coordination to the silver ions, are crystallized in the fully extended all-trans conformation. Interestingly, though all compounds are crystallized in a monoclinic crystal system, their lateral chain packing, van der Waals effects, and hence vibrational features are chain length-dependent. This is a direct result of electrostatic effects of the COO group in addition to vibrational coupling between CH2, CH3, and COO modes, an effect which varies significantly with chain length. Variable temperature infrared measurements indicate significant irreversible changes in the metal-carboxyl coordination sphere, most likely due to bond fission. For long chain adducts (nc>12), thermally induced crystal system switching, monoclinic to triclinic, indicates greater thermal sensitivity of their alkyl chains. During heating, the regions of the hydrocarbon chains, furthest from the COO, become increasingly molten and mobile as the stepwise melt advances towards the solid COO moieties. This solid-liquid melting behaviour is responsible for mesophase formation in metal carboxylate systems.

Multiple surface interaction mechanisms direct the anchoring, co-aggregation and formation of dual-species biofilm between Candida albicans and Helicobacter pylori

“…Likewise, for amino acids, shifts of wavenumbers would be expected since they have non-polar short chains. Similarly, it has been reported that the displacements of the signals associated with CH bonds are related to molecular packaging [64] , [65] ; thus, a decrease in packing will be associated with greater freedom of movement and consequently greater vibrational energy (displacement of signals at higher wavenumbers) [65] . The above is important because a weakening of the yeast cell envelope of C. albicans , due to the presence of H. pylori , could manifest itself in a shift to larger wavenumbers; likewise, a restriction of freedom of movement would be associated with shifts to lower wavenumbers.…”

“…In relation with the mechanism 1, it has been reported that the union of alkyl groups to polar groups, e.g., carbonyl, is affected in their vibratory movements as a function of the length of the alkyl chain [64] . In this way, for shorter chain length is greater the effect of polar groups, and conversely, as the chain length increases, the vibratory movements become independent of the influence of polar groups.…”

Electron-Induced Decomposition of Different Silver(I) Complexes: Implications for the Design of Precursors for Focused Electron Beam Induced Deposition

“…The transmission IR spectra of Ag(I) 2,2-dimethylbutanoate ( Figure 3 a) and Ag(I) benzoate ( Figure 3 b) obtained from the as-synthesised compounds agree well with previous results [ 21 , 37 , 38 , 39 ]. However, the positions of the asymmetric carboxylate stretching vibration ν as (COO − ) at 1544 and 1553 cm −1 are indicative of a dominant contribution of ligands with a monodentate coordination [ 40 , 41 , 42 , 43 ]. The transmission IR spectrum of Ag(I) benzoate exhibits an additional band at 1517 cm −1 , which is characteristic of a bridging coordination [ 40 , 41 , 42 , 43 ].…”

“…However, the positions of the asymmetric carboxylate stretching vibration ν as (COO − ) at 1544 and 1553 cm −1 are indicative of a dominant contribution of ligands with a monodentate coordination [ 40 , 41 , 42 , 43 ]. The transmission IR spectrum of Ag(I) benzoate exhibits an additional band at 1517 cm −1 , which is characteristic of a bridging coordination [ 40 , 41 , 42 , 43 ]. Only the bridging coordination is observed in the ATR–IR and RAIR spectra of both Ag(I) 2,2-dimethylbutanoate and Ag(I) benzoate.…”

The Impact of an Anchoring Layer on the Formation of Tethered Bilayer Lipid Membranes on Silver Substrates

“…There has already been discussion of these modes being largely from the alkyl chains of the WC14 rather than the EO segment, [4,31] allowing the analysis of the conformational order of the hydrophobic WC14 chains independent of EO. Highly ordered crystalline Ag-adsorbed alkanes have their ν s and ν as methylene vibrations at around 2847 and 2916 cm -1 [32]. A departure to the higher wavenumbers from those positions attests to the increase in structural flexibility and gauche defects.…”