Four different complexes of the cobalt(II) acetate–pyridine–water system were obtained as dominant species by crystallization from a series of dichloromethane and toluene solutions. The complexes were characterized by terms of X-ray crystal structure determination. Factors in solution properties leading to crystallization of certain complexes are discussed. Furthermore, trends in terms of structure and binding energies in a systematic series of mononuclear cobalt(II) complexes were studied using density functional calculations.

A series of synthetic polymers were designed and synthesized for enhancing the rate of the Diels-Alder cycloaddition reaction of 1,3-butadiene carbamic acid benzyl ester (11) and N,N-dimethyl acrylamide (2), to yield the corresponding endo- (3) and exo- (4) reaction products. Putative transition state analogues (TSAs) for the endo- (5) and exo- (6) reaction pathways were used as templates for the synthesis of molecularly imprinted methacrylic acid (MAA)-divinylbenzene (DVB) copolymers. The polymer system utilized was selected based upon a series of (1)H NMR studies of complex formation between template and a functional monomer analogue (K(d) (app) approximate to 70 mM, d(8)-toluene, 293 K). Batch binding studies revealed that the imprinted polymers were selective for the TSA corresponding to the template used in the polymer synthesis. Studies on the influence of the polymers on the catalysis of the reaction of 1 and 2 demonstrated a 20-fold enhancement of the rate of the reaction relative to the solution reaction. A surprising temperature dependence of the reaction of 1 and 2 in the presence of the polymers was observed, which provides support for the role of template-functional monomer complexes in the catalysis of the Diels-Alder reaction.

Here we present a series of molecularly imprinted polymers capable of catalysing the Diels-Alder reaction between benzyl 1,3-butadienylcarbamate (1) and N,N-dimethyl acrylamide (2). The polymer systems studied here demonstrated an unusual cross-linker and temperature dependent behaviour, namely that polymer catalysis of the Diels-Alder reaction was lower at elevated temperature, in contrast to the solution reaction. Furthermore, not only was the catalytic activity significantly influenced by the choice of cross-linker, but in a similar fashion also the extent of the temperature effect, indicating a close relationship between catalysis and the observed inhibition. Molecular dynamics simulations of both the polymer systems studied were used to provide insight into the molecular background of transition state stabilisation, and differences in properties of the systems based on different cross-linkers.

The anticoagulent drug warfarin exhibits chameleon-like isomerism, where the environment-dependent composition of the ensemble of structures greatly influences its bioavailability. Here, the mechanism of conversion between the major isomeric forms is studied. The dramatic differences in transition state energies, as determined by density functional calculations, highlight the necessity for the involvement of intermolecular interactions in the key proton transfer step. A viable model for the mechanism underlying the isomerization reactions is presented.