Twelve Ir(iii) triscyclometalated compounds containing up to three azobenzene fragments on their structure have been synthesized based on photochromic 2-phenylpyridyl type ligands . These complexes are intended to study the possibility of transferring the photochromicity of the azobenzene fragment to the organometallic compound, and the effect of the substitution pattern, relative distance of the azobenzene to the metal centre, and number of azobenzenes on their properties.

A new synthetic route toward photochromic azobenzeneappended bipyridyl ligands has been developed, and 20 new cationic iridium(III) bis-cyclometalated complexes containing up to four azobenzene fragments on their structure have been synthesized and characterized electronically and spectroscopically. These compounds incorporate photochromic azobenzene units in their neutral pyridyl ligands 1−5, and in four of them azobenzenes have been also introduced a posteriori on their phenylpyridyl ligands by palladium-catalyzed cross-coupling. UV−vismonitored light-triggered trans-to-cis isomerization of the azobenzeneappended ligands revealed a strong inhibition of this process upon coordination to the d 6 -metal ion. TD-DTF calculations revealed that this inhibition could be a consequence of a metal to ligand charge transfer relaxation process.

The use of the readily available complex [Ru(p-Cym)(bipy)Cl]Cl as an efficient and robust precatalyst for homogeneously catalysed solvolysis of amine-borane adducts to liberate the hydrogen content of the borane almost quantitatively is being presented. The reactions can be carried out in tap water, and in aqueous mixtures with non-deoxygenated solvents. The system is also efficient for the dehydrocoupling of dimethylamine-borane under solvent-free conditions.

Iridium(iii) cyclometalated complexes have been used as models to study the effect that extended conjugation and substitution pattern has on the photochromic behavior of azobenzene-appended 2-phenylpyridyl (ppy) ligands. For this purpose four azobenzene-containing ppy ligands were synthesized. With these ligands, nine iridium(iii) complexes containing up to three appended azobenzenes were synthesized. Analysis of their photochromic behaviour by means of UV-vis and (1)H-NMR spectroscopy permitted us to conclude that the light-induced trans-to-cis isomerization of the azobenzene was strongly inhibited upon coordination to the Ir(iii) cation when the electronic conjugation was extended along the whole ligand. The use of an aliphatic spacer unit (either -CH2- or -OCH2-) between the azobenzene and the ppy fragment of the ligand sufficed to disrupt the electronic communication, and obtain photochromic organometallic complexes.