General, efficient and inexpensive methods for the synthesis of dendritic building blocks methyl 3',4'-dihydroxybiphenyl-4-carboxylate, 3',5'-dihydroxybiphenyl-4-carboxylate, and methyl 3',4',5'-trihydroxybiphenyl-4-carboxylate were elaborated. In all syntheses the major step involved an inexpensive Ni(II)-catalyzed Suzuki cross-coupling reaction. These three building blocks were employed together with methyl 4'-hydroxybiphenyl-4-carboxylate in a convergent iterative strategy to synthesize seven libraries containing up to three generations of 3',4'-, 3',5'-, and 3',4',5'-substituted biphenyl-4-methyl ether based amphiphilic dendrons. These dendrons self-assemble into supramolecular dendrimers that self-organize into periodic assemblies. Structural and retrostructural analysis of their assemblies demonstrated that these dendrons self-assemble into hollow and non-hollow supramolecular dendrimers exhibiting dimensions of up to twice those reported for architecturally related dendrons based on benzyl ether repeat units. These new dendrons expand the structural diversity and demonstrate the generality of the concept of self-assembling dendrons based on amphiphilic arylmethyl ethers.
Porous polyhedral silsesquioxane (POSS)-based network polymers are prepared using hydrosilation copolymerisation reactions of a silyl-functionalised POSS molecule with a vinyl-functionalised moiety. Characterisation of these solids show them to possess pore structures in the mesoporous regime, and polymers with longer organic linking groups showing evidence of flexible wall structures. Functionalisation of the polymers is carried out by reaction with triflic acid or sodium hydroxide, followed by incorporation of CpTiCl 3 . EXAFS spectroscopy results are consistent with the titanium being coordinated to the oxygen atoms that make up part of a POSS unit.
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