Photoinduced linkage isomerism of {RuNO}6 complexes with bioligands and related chelators

Abstract

Five novel complexes containing the {RuNO}⁶ fragment and the anions derived from L-histidine (L-his), rac-3-amino-alanine (rac-dap), kojic acid (koj), methyliminodiacetic acid (mida), and thiodiacetic acid (tda) have been synthesised and characterised by single-crystal X-ray diffraction analysis, mass spectrometry, spectroscopic methods (NMR, UV–vis, IR) and elemental analysis. In the irradiated complexes, [Ru(NO)Cl₂(L-his)] (1), [Ru(NO)Cl₂(rac-dap)] (2), K[Ru(NO)Cl₃(koj)] (3), K[Ru(NO)Cl₂(mida)]·½H₂O (4), and K[Ru(NO)Cl₂(tda)]·H₂O (5), the existence of the photoinduced long-lived metastable isonitrosyl state S1 and/or the side-on-bonded S2 state were detected by differential scanning calorimetry (DSC) and/or IR spectroscopy. For all complexes 1–5 full geometry optimisation, frequency analysis and calculation of the isotropic magnetic shielding tensors have been conducted in the framework of DFT theory.