Thermal behavior of some N,N-dimethylbiguanide derivatives displaying antimicrobial activity

N,N-Dimethylbiguanide derivatives (HDMBG)X, where X=CH₃COO (1), Cl (2) and NO₃ (3) respectively, exhibit in vitro antimicrobial activity on representative bacterial and fungal strains. The presence of N,N-dimethylbiguanidium ion for all derivatives was evidenced by IR and ¹H NMR spectra. Thermal analysis gave information on their decomposition steps and also on the accompanying thermodynamic effects. According to TG and DTG curves processes as melting, oxidative degradation as well as oxidative condensation of –C=N– units occur. The different nature of the anions results different melting points. Paracyanide formation at various condensation degrees was observed.     

Charge transfer interactions in polyesters with a donor‐(σ‐bridge)‐acceptor moiety in the repeating unit

Two high molecular weight linear polyesters were investigated to gain insight in how the photophysics of electron donor‐(σ‐spacer)‐electron acceptor (DσA) compounds are affected by incorporation into a polymer. They were prepared by condensation of either adipoyl or sebacoyl chloride with a diol that was functionalized with an N,N‐dialkylaniline donor, a cyclohexyl type σ‐spacer, and a 1,1‐dicyanovinyl acceptor. The solubility, which is very low, and the thermal properties of the polyesters are dictated by physical crosslinking as a consequence of interchain donor‐acceptor interactions. Charge transfer (CT) absorption and emission are observed, which involve CT between DσA moieties of different chains rather than CT processes within a single DσA unit. As a result, the photophysics of the DσA units in the polyesters differs strongly from that of similar DσA compounds in solution. Upon swelling the polymers with THF, the CT fluorescence disappears partly. Analogous polymers containing only an N,N‐dialkylaniline donor display dual fluorescence; one band reflects local emission, while the other is attributed to excimer emission. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4775–4784, 2004     

Cobalt–Pincer Complexes in Catalysis

Non-noble metal catalysts based on pincer type compounds are of special interest for organometallic chemistry and organic synthesis. Next to iron and manganese, currently cobalt–pincer type complexes are successfully applied in various catalytic reactions. In this review the recent progress in (de)hydrogenation, transfer hydrogenation, hydroboration and hydrosilylation as well as dehydrogenative coupling reactions using cobalt–pincer complexes is summarised.     

Geometric structure of b2,2-orbihedra and interpolation of operators

We compute the normals to faces of b_2,2-orbihedra and apply the results to Operator Interpolation Theory.