From Dipolar to Octupolar Phthalocyanine Derivatives: The Example of Subphthalocyanines.

Boron-subphthalocyanines (SubPcs)—cone-shaped 14-π electron aromatic macrocycles—are lower phthalocyanine analogues which consist of three isoindole units N-fused around a central boron atom which fourth valency is occupied by an axial ligand. SubPcs have been shown to possess very interesting features for NLO. Although they present a permanent dipole moment along the boron-axial substituent axis, their optical response is essentially associated to charge transfer inside the macrocycle π-surface. Moreover, due to the C3v symmetry of the SubPc core, its NLO behavior is mostly octupolar. It will be shown that the application to SubPcs of the design criteria that have been successful in phthalocyanines and porphyrins led to high-performance second-harmonic generators [ABSTRACT FROM AUTHOR]