Quadrupole hydrogen bonding

Figure 1.4 Synthesis of a monofunctional 2-ureido-4[lH]-pyrimidinone (UPy) (1) and dimerization of 1 in solution forming a quadrupole hydrogen-bonded unit. (After Sijbesma et al., 1997.)...

Ercolani G. Comment on SelTassembled multipotphytin arrays mediated by selT complementary quadrupole hydrogen bond motifs . Chem Commun. 2001 1416—1417. 

The quadrupole hydrogen-bonded unit can be employed in the chain extension of telechelic ohgomers such as polysiloxanes, polyethers, polyesters, and polyacrbonates (Fohner et al., 2000). Thus the electrophilic isocyanate group (-NCO) of synthon (3 in Fig. 1.5) can be reacted with common nucleophilic end groups (-OH or -NH2) of telechelic ohgomers, resulting in supramolecular polymers by chain extension (Fig. 1.6). Thus the material properties of telechelic polymers have been shown to improve dramatically upon functionahzation with synthon, and materials have been obtained that combine many of the mechanical properties of conventional macromolecules... 

Further, in the case of virtually non-existent ion-solvent interactions (low degree of solvation), so that solute-solute interactions become more important, Kraus and co-workers47 confirmed that in dilute solutions ion pairs and some simple ions occurred, in more concentrated solutions triple ions of type M+ X M+ orX M+X andinhighly concentrated solutions even quadrupoles the expression triple ions was reserved by Fuoss and Kraus48 for non-hydrogen-bonded ion aggregates formed by electrostatic attraction. 

That way, the Distributed Electrostatic Moments based on the ELF Partition (DE-MEP) allows computing of local moments located at non-atomic centres such as lone pairs, a bonds and n systems. Local dipole contributions have been shown to be useful to rationalize inductive polarization effects and typical hydrogen bond interactions. Moreover, bond quadrupole polarization moments being related to a n character enable to discuss bond multiplicities, and to sort families of molecules according to their bond order. 

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