Azadipyrromethene Complexes of d⁸ Metal Centers: Rhodium(I), Iridium(I), Palladium(II), and Platinum(II)

Abstract

Azadipyrromethenes are blue pigments that chelate main-group and d-block Lewis acids. Reported here are azadipyrromethene complexes of d(8) metal centers. The new compounds are prepared in salt metathesis reactions with chlorinated organometallic precursors. Sixteen new complexes are reported. The principal absorption features are an intense peak near 600 nm and transitions in the ultraviolet; all are characteristic of the azadipyrromethene chromophore. All compounds are dark solids that yield blue or blue-violet solutions. Ten complexes are crystallographically characterized. The structures uniformly show backbone strain, with a meso-nitrogen atom that dilates from pure sp(2)-hybridization. Structural comparisons are made to related dipyrromethene and tetra-azaporphyrin complexes. The electron-donating capacity of azadipyrromethene ligands is evaluated from C≡O stretching frequencies of three rhodium(I) carbonyl complexes and from density-functional theory calculations. Frontier orbitals are confined to the azadipyrromethene ligand. HOMO-LUMO energy gaps are almost unperturbed from those of the free, anionic azadipyrromethene.

Azadipyrromethenes: from traditional dye chemistry to leading edge applications

“…[36][37][38][39][40][41][42][43][44][45][46] Typically, complexes are formed under mild rt conditions in THF with t-butoxide or DIPEA as base. This points to an ever expanding future for these complexes not just for their own inherent properties but also for catalysis and material applications.…”

A novel silver(I)-selective PVC membrane sensor and its potentiometricapplications

“…Several studies showed that azadipyrromethenes might chelate with d-block elements through pyrolic nitrogens. 16 In a study published by the Gray group in 2007, tetraarylazadipyrromethene compounds were shown to form heteroleptic complexes with silver and other d 10 metals. 17 The ability of azadipyrromethene to bond with metal centers indicates that these compounds have the potential to be used as ionophores in the structure of ion-selective electrodes.…”

Molecular excitons in a copper azadipyrrin complex

“…7,11 (Aza)dipyrrins exhibit rich coordination chemistry with a wide variety of transition metal species. 7,[12][13][14][15][16][17][18][19] In transition metal species with multiple (aza)dipyrrin ligands, the large transition dipole moment of the π-π* generates coupling between the π-π* states which leads to the formation of excitonic states in metallodipyrrin species. [20][21][22] Exciton coupling theory assumes dipole-dipole coupling between the π-π* states of the chromophores.…”