Terpyridine Zn(II), Ru(III), and Ir(III) Complexes:  The Relevant Role of the Nature of the Metal Ion and of the Ancillary Ligands on the Second-Order Nonlinear Response of Terpyridines Carrying Electron Donor or Electron Acceptor Groups

Abstract

Coordination of 4'-(C6H4-p-X)-2,2':6',2''-terpyridines [X = NO2, NBu2, (E)-CH=CH-C6H4-p-NBu2, (E,E)-(CH=CH)2-C6H4-p-NMe2] to Zn(II), Ru(III), and Ir(III) metal centers induces a significant enhancement of the absolute value of the second-order nonlinear optical (NLO) response of the terpyridine, measured by means of both electric field induced second harmonic generation and solvatochromic methods. By varying the nature of the metal center, the enhanced second-order NLO response shifts from positive to negative. Such a shift is controlled by electronic charge-transfer transitions, such as metal-to-ligand or ligand-to-metal transitions, in addition to the intraligand charge transfer. The enhancement generated by coordination is also controlled by the chelation effect and by fine-tuning of the ancillary ligands.

Recent Developments in the Application of Phosphorescent Iridium(III) Complex Systems

“…[97][98][99][100][101][102][103][104] A detailed review about this concept has recently been published by Williams et al [105] Iridium(III) mono-terpyridine complexes decorated with electron-donor or -acceptor groups have furthermore been employed as asymmetric chromophores in nonlinear optics. [106,107] By introducing strong ligand-field-stabilizing ligands, such as CN À or CO, the energy gap between the HOMO and LUMO can be significantly increased resulting in anionic or cationic iridium(III) complexes with bright blue emission. Recent examples by Fantacci and Nazeeruddin and their co-workers [108,109] as well as Chin et al [110] have nicely expanded the toolbox of color-tuning in iridium(III) complexes (Scheme 2).…”

A Joint Experimental and Theoretical Investigation on Nonlinear Optical (NLO) Properties of a New Class of Push–Pull Spirobifluorene Compounds

“…We were able to prepare compounds with a range of conjugation lengths through several palladium-catalyzed cross-coupling reactions between 8 and a suitable amino intermediate. In order to estimate the influence of the electronic connection between the acceptor and donor moieties in the spirobifluorene spacer itself, we synthesized 2,2Ј-dinitro-7,7Ј-dipiperidin-1-yl-9,9Ј-spirobifluorene (1) 4 ] as catalyst and aqueous K 2 CO 3 as base, provided an easy way to interpose a single phenyl ring between the donor and acceptor groups. The reaction of 8 with 4-(N,N-diphenylamino)phenyl boronic acid (9) afforded 2,2Ј-dinitro-7,7Ј-bis(4-N,N-diphenylaminophenyl)-9,9Ј spirobifluorene (2) in 77 % yield.…”

ZnII–2,2′:6′,2″‐Terpyridine‐Based Complex as Fluorescent Chemosensor for PPi, AMP and ADP

“…[15] This was subjected to the free radical bromination reaction using NBS as the brominating agent. [16] 4Ј-[p-(Bromomethyl)phenyl]-2,2Ј:6Ј,6ЈЈ-terpyridine was isolated in reasonably good yield and was allowed to react with presynthesized 7-hydroxy-4-methylcoumarin in the presence of K 2 CO 3 and a catalytic amount of 18-crown-6 in dry acetone to yield L 1 in reasonable yield (Scheme 1). [17] This was allowed to react with Zn(ClO 4 ) 2 at room temperature to yield the desired compound.…”