ABSTRACT
How strong are van der Waals interactions in determining the final outcome of self-assembled structures of small molecular systems? Herein we report isolable phthalocyanine (Pc) dimers bound by π-π interactions between monomeric Pcs which can be handled as single entities. Pc dimers have been continuously investigated as one of the simplest models of Pc aggregates. Pcs were substituted with eight dihydrodiazapentacene (DHDAP) moieties on the periphery, which act as pillar-like π-planes and these molecules form H-type dimers with the help of synergetic π-π interactions between two co-facial Pc rings and among the pillar-like DHDAP moieties. The dimer structures were fully confirmed by 1D and 2D NMR, ESR, and electronic absorption measurements. The dissociation of these dimers was observed in particular solvents such as o-dichlorobenzene, due to the good solubility of the larger π-conjugated molecules. On the other hand, in ethyl acetate the monomers were metastable species and underwent selective dimerization. Interestingly in THF, neither the dimerization of the monomers nor the dissociation of dimers was observed, suggesting that both the dimers and the monomers were kinetically well stabilized. For hours to days, we can handle these dimers as "a molecule" not only in solution but also even in mass spectrometry under ionization conditions without significant dissociation.
ABSTRACT
A series of peripherally dicyano-, tricyano-, and tetracyano-substituted subphthalocyanines (SubPcs) have been prepared through microwave-assisted, palladium-mediated cyanation of iodinated precursors. The introduction of π-accepting cyano groups in the macrocycle clearly influences its electronic and redox properties, which are dependent on the number and relative position of these substituents. Additional functionalization of the periphery of SubPcs with electron-donating or -withdrawing groups allows for a further fine-tuning of their features, leading to intensely absorbing, strongly electron-accepting panchromatic dyes with low-lying LUMO energy levels. Flash-photolysis time-resolved microwave conductivity measurements on vapor-deposited films demonstrate that some of these novel SubPc derivatives display remarkable intrinsic charge-carrier mobilities that are comparable to or larger than those of other known well-performing acceptor SubPcs; thus confirming their potential as n-type organic semiconductors for application in the fabrication of photovoltaic devices.
