Template effect negative

According to the opinion of the authors of Ref. 32, the negative results of the experiments above do not mean that metal-free Pc could not be theoretically obtained from these precursors additional detailed studies (combination of different techniques, such as UV irradiation, microwave treatment, use of other inert solvents, electrolysis in the systems producing free radicals, etc.) are required for successful resolution of this problem. However, under the same conditions it is possible to obtain some transition metal complexes of the Pc due to the template effects (see below). 

In the use of templates, Sanders and co-workers [47] differentiate between two modes of action that are complementary a positive template directs the approach of two reactive end groups in a molecule, thereby generally supporting the desired intramolecular cyclization. In contrast, a negative template effect holds the reactive groups apart, thereby suppressing the intramolecular cyclization and leading preferentially to the (undesired) intermolecular reaction. 

Fig. 3. Dynamin s liposome-stimulated GTPase activity varies with liposome composition. (A) Dynamin s GTPase activity is greater when assayed in the presence of liposomes composed exclusively of DOPS, compared to liposomes prepared from DOPC PI4,5P2 (90 10 mol%). Liposomes composed of a higher mol% PI4,5P2 (see Fig. 2) are significantly more effective templates. (B) Negative-stain electron micrographs of dynamin-generated lipid tubules formed on DOPS and DOPC PI4,5P2 liposomes are indistinguishable, despite the observed differences in rates of GTP hydrolysis. Scale bar = 50 nm.

Figure 1-2. Schematic illustration of positive and negative template effects in directed synthesis of chemical species.

The equilibrium composition of the imprinted gel, assuming that there are no network defects apart for incomplete saturation of the functional sites of the templates, is obtained by solving Eqs. 7-12. Different materials and preparation conditions are modeled through the interactions parameters which is related to the excluded volume of the monomers, and Xf, which is a measure of the difference in the interactions between the different materials (monomers and templates) and is proportional to the inverse of the temperature [26]. Xf vanishes when the interactions are similar in magnitude, it is negative when the interactions are unfavorable, and it is positive when the interactions are favorable. Thus, different values of the interaction parameters effectively correspond to different preparation conditions defined by the temperature and solvent. 

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