Hetero-association

S. Lomas, Self and hetero association of sterically hindered tertiary alcohols. J. Phys. Org. Chem. 18, 1001 1012 (2005). 

With controllable strength of the self- and hetero-associated hydrogen, a molecular level penetrated semi-interpenetrating polymer networks (semi-IPNs) of ST-VPDMS with poly(N-vinylpyrrolidone) (PVPr) were prepared by condensation of the self-associated silanols.13... 

The same research group also reported the hetero-association of phthalocyanines 108 with 109 as well as 108 with 110, both of which are stabilized by donor-acceptor interactions [89], Compounds 108 and 109 were prepared by standard... 

The ZnPc-Cgo dyad 110 has a low fluorescence quantum yield (f = 0.01) in toluene due to the intramolecular electron-transfer deactivation. Addition of 108 leads to a further reduction in the fluorescence intensity (4>f = 0.002) and a slight blue shift of the emission maximum, suggesting the formation of the ensemble 108-110, in which the two components have strong excitonic coupling. The addition of 108 (i.e. the hetero-association) also stabilizes the radical ion pair ZnPc+-C6o, increasing the lifetime from 130 ns (for 110) to 475 ns (for 108-110) (measured in tetrahydrofuran). 

Solute-solvent interactions in dithiole-thiones and -ones are attributed to localized electrostatic induction. The strength of the hetero-association complexes is determined by the distribution of the electric field around the carbonyl or thiocarbonyl group (72HCA213). 

As discussed in Chapter 15, the arrangement of the functional groups on adjacent ring positions in the purine and pyrimidine bases is such as to increase the strength of hydrogen bonding due to 7i-cooperativity. This favors the formation of base-paired dimers and in some cases of trimers and tetramers. These can occur between the same bases (homo- or self-association) and between different bases (hetero-association). 

Base-Pair Configurations with Purine-Pyrimidine Hetero-Association... 

Matrix isolation vibrational spectroscopy is simpler and easier to apply but is sometimes not as powerful as tl previous method. Althou not free of various difftculties and shortcomings (in particular, the extent of into-actions between the vdW system and the atoms (molecules) of the matrix is not clear), this type of spectroscopy is a useful tool for investigation of hydrogen bonded complexes (self-association and hetero-association) and of molecular (charge-transfer) com-plexes ... 

UCacil derivatives associate ith each other, though the interactions are weak ccsypared with that of the A-U association. Self-association is here treated in the same way u hetero-association. The eqllibrlum relation for self-association is expressed as follows... 

The first system we study is a mixture of R Ai and R Bi chains, each carrying a functional group A or B at one end. Diblock copolymers are formed by the end-to-end association (hetero-dimerization) [1,2]. End groups A and B are assumed to be capable of forming pairwise bonds A-B by thermoreversible hetero-association. The hydrogen bond between acid and base pair is the most important example of this category. 

The same D-A recognition motif was further exploited by Torres and Guldi in the construction of photoactive supramolecular Pc-Ceo triads. Hetero-association between the complementary electron-deficient Pc 6 and electron-rich Pc 7, bearing also a covalently linked Ceo unit, was confirmed by different techniques, which provided evidence for the formation of a 1 1 D-A complex with a stabiUty constant of about 10 in chloroform (Figure 5). Moreover, the radical-ion-pair... 

The first step of the study was the investigation of the solution behaviour of the synthetic drag molecules alone prior to their complexation with DNA. Investigations of the self- and hetero-association of biologically active compounds... 

The shift of the miscibility window would be expected due to the increased strength in hetero-associated hydrogen bonds and the reduced strength in the silanol self-associated hydrogen bonds in ST-VPMPS/PBMA blends. 

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