A family of readily synthesised phosphorescent platinum(ii) complexes based on tridentate N^N^O-coordinating Schiff-base ligands

Abstract

Tridentate ligands, easily synthesised by condensation reactions of simple starting materials, can be used to prepare Pt(ii) complexes that are luminescent in solution, emitting in the red or deep-red spectral region, according to the substituents.

Differences in Stability, Cytotoxicity, and Mechanism of Action of Ru(II) and Pt(II) Complexes of a Bidentate N,O Donor Ligand

“… , The aim of the present study is to investigate the effect of the variation of the metal center between Ru­(II) and Pt­(II), by keeping the same chloroethylamine motif bearing ligand(s), since Pt­(II) complexes containing this particular moiety are scarce − and Ru­(II) complexes of the same are not known. However, Pt­(II) or Ru­(II)- p -cymene complexes of various other salicylaldimine based ligands have shown anticancer activity, stabilization of telomeres, and efficiency in catalysis. − In addition, earlier works show that using one ligand and varying the metal center (Ir, Ru, or Rh) has a substantial impact on the solution stability and also alters the cytotoxicity of a resultant complex against a particular type of cancer. − …”

Mono and dinuclear iridium(iii) complexes featuring bis-tridentate coordination and Schiff-base bridging ligands: the beneficial effect of a second metal ion on luminescence

“…23 In our previous work investigating Pt(II) complexes of this ligand, and derivatives with substituents in the aromatic rings, we found that the resulting Pt(N^N^O)Cl complexes had poor stability, displaying quite rapid light-induced decomposition in solution, compromising the emission properties and rendering them difficult to assess. 21 The instability was apparently associated with the facile deprotonation of the hydrazone unit. In contrast, complexes of the corresponding N-methylated ligands were robust, with no evidence of decomposition.…”

“…10a The higher molar absorptivities in the present case no doubt reflect the introduction of additional transitions associated with the hydrazone ligand, as observed in the previously reported Pt(II) complexes of these ligands, where d M |π ArO → π* py character is invoked. 21 The introduction of an electron-donating methoxy group para to the phenolate oxygen leads to a distinctive red-shift in the lowest-energy band. As in the Pt(II) complexes, this can be readily understood in terms of an increase in electron density in the metal/phenolate filled orbitals, reducing the frontier orbital gap and hence the energy of the transition to the vacant π* orbitals.…”

“…Proligands HL 1 -HL 4 were prepared by condensation of N-methylhydrazinopyridine with the appropriate salicylaldehyde, as described in our earlier work on Pt(II) complexes. 21 Starting materials for the preparation of the ditopic ligands were obtained from commercial suppliers and used as supplied. Details are given below, and the numbering system for the assignment of NMR resonances is provided in Fig.…”

“…Recently, we showed that proligands based on N-methyl-N-(2-pyridyl)-N′-(salicylidene)hydrazonereadily prepared from low-cost salicylaldehydes and 2-hydrazino-pyridines by simple Schiff-base condensation reactionscan be coordinated to Pt(II) to generate compounds of the form [Pt(N^N^O)Cl]. 21 These complexes are phosphorescent in solution under ambient conditions, and emission is further enhanced by metathesis of the monodentate halide to an acetylide, [Pt(N^N^O)(CuC-Ar)]. It was of interest to examine whether such ligands could be used successfully with iridium(III), in combination with N^C^N-coordi-nating ligands, to generate new emissive materials.…”