Porphyrins for Second Order Nonlinear Optics (NLO): An Intriguing History §

Abstract

This short review outlines the main results obtained by our research group over the last 15 years in the field of porphyrins and metal porphyrins for second order nonlinear optics (NLO). This overview aims to provide a general framework of the key factors which affect the second order NLO response of porphyrin chromophores. The pivotal role of the porphyrin ring as π-conjugated linker, the nature of the metal center, the substitution pattern which features the geometrical arrangement of donor and acceptor substituents in the different classes of porphyrin NLO-phores, as well as the aggregation phenomena and the role of solvents are addressed in detail.

Cyclometalated Ir(III) Complexes with Curcuminoid Ligands as Active Second-Order NLO Chromophores and Building Blocks for SHG Polymeric Films

“…Coordination compounds also showed promise because they were characterized by low-energy ligand-to-metal (LM), metal-to-ligand (ML), ligand-to-ligand (LL), and intraligand (IL) charge transfer (CT) excited states. The intensity and energy of these transitions can be easily regulated by a judicious choice of the nature, oxidation state, and ligands of the metal center [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

Electric-Field-Induced Second Harmonic Generation Nonlinear Optic Response of A4 β-Pyrrolic-Substituted ZnII Porphyrins: When Cubic Contributions Cannot Be Neglected

“…In particular, metal complexes of macrocyclic ligands with a large π electronic system such as porphyrins have been largely investigated, because when their structures are characterized by a specific asymmetric push–pull arrangement a significant directional charge transfer process involving π-polarizable linkers is produced by connecting the donor−π–acceptor system, and significant values of the quadratic hyperpolarizability β are achieved (which is the figure of merit of the second-order NLO response). 1 − 3 Moreover, the porphyrin ring is a flexible electronic system, where electron-rich (β-pyrrolic) and electron-poor ( meso ) carbon atoms can be identified. 2 …”

A Chiral Bis(salicylaldiminato)zinc(II) Complex with Second-Order Nonlinear Optical and Luminescent Properties in Solution

“…In fact, an important requirement for second-harmonic generation (SHG) applications is transparency in a large spectral range in order to avoid absorption of the second harmonic [43]. Many zinc compounds having nitrogen-donor ligands such as monodentate stilbazole [44][45][46], bidentate bipyridine [26,[47][48][49][50][51][52] or phenanthroline [44,53], tridentate terpyridine [54][55][56] or tetradentate porphyrin [57][58][59], characterized by a good second-order NLO response, have been reported, whereas the great potential of bis(salicylaldiminato)zinc Schiff base complexes [60][61][62][63] has recently been the subject of a deep exploration.…”