Donor−Acceptor Biomorphs from the Ionic Self-Assembly of Porphyrins

Abstract

Microscale four-leaf clover-shaped structures are formed by self-assembly of anionic and cationic porphyrins. Depending on the metal complexed in the porphyrin macrocycle (Zn or Sn), the porphyrin cores are either electron donors or electron acceptors. All four combinations of these two metals in cationic tetra(N-ethanol-4-pyridinium)porphyrin and anionic tetra(sulfonatophenyl)porphyrin result in related cloverlike structures with similar crystalline packing indicated by X-ray diffraction patterns. The clover morphology transforms as the ionic strength and temperature of the self-assembly reaction are increased, but the structures maintain 4-fold symmetry. The ability to alter the electronic and photophysical properties of these solids (e.g., by altering the metals in the porphyrins) and to vary cooperative interactions between the porphyrin subunits raises the possibility of producing binary solids with tunable functionality. For example, we show that the clovers derived from anionic Zn porphyrins (electron donors) and cationic Sn porphyrins (electron acceptors) are photoconductors, but when the metals are reversed in the two porphyrins, the resulting clovers are insulators.

Diffusion controlling porphyrin assembled structures

“…In the field of self-assembly, the assembled structures also present the feature of diversity [13][14][15]. A slight change of assembling condition makes the structures of products totally different [16][17][18].…”

Supramolecular hetero-porphyrin SWNT complexes

“…We found that much more of 3 must have been desorbed according to the UV-vis spectra of the released porphyrins. Normally, the mixing of cationic and anionic porphyrins is forms 1:1 mixtures [19,25]; cyclic voltammery has suggested this to be the case for our system also (vide infra), demonstrating that the desorption of the different porphyrins is solvent dependant. In the case of 1/3-SWNT, almost equimolar amounts of 1 and 3 were obtained from the stripping of the SWNTs.…”

“…In particular, the combination of a cationic and an anionic porphyrin leads to a very high loading (>200 nmol per mg SWNT) through electrostatic interactions. This system can be regarded as a supramolecular extended co-operative binary ionic (CBI) solid [19]; these materials are of high interest in electronic applications.…”

Electrosynthesis Processes Based on Oxidative Couplings of Porphyrins for the Formation of Supramolecular Assemblies

“…[1][2][3][4][5][6][7][8] Even if the formation of dimers or trimers of porphyrins is principally described, it is interesting to mention the work of Shelnutt and coworkers who have obtained original electrostatic self-assembled multi-porphyrin nanostructures. [9][10][11][12] Indeed, depending on the central metal (Zn or Sn), the porphyrins are either electron donors or electron acceptors, respectively, and thus nanotubes and clover-shaped nanostructures can be formed (see Figures 2A and 2B).…”