Follow-up study of Trans-C to Cis-C Thermally or Photochemically Induced Isomerisation of Terpyridine Adducts of Cycloruthenated 2-aryl-2'-pyridine Compounds

• Published in: Inorganic chemistry 2024, Vol.63 (11), p.4867-4874
• Main Authors: Ali, Moussa, Cornaton, Yann, Djukic, Jean-Pierre, Pfeffer, Michel
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Coordination chemistry
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c03671

The mechanism of isomerization of the known 2-phenyl,pyridine (phpy) derivatives [Ru(phpy-$K$C,N) (MeCN-trans-N)(terpy)]PF6 , 2, to [Ru(phpy-$K$C,N)( MeCN-trans-C)(terpy)]PF6 (terpy = 2,2';6',2"-terpyridine), 3, at temperatures > 50°C has been investigated both by $^1$H NMR spectroscopy and by DFT calculations. The photoisomerization of 2 to 3 by UV light occurred also quantitatively in MeCN after 20h at room temperature. A similar behavior to that of 2, could be established for the related compound [Ru(3-acridine-2′-C5H4N-$K$C,N)( MeCN-trans-N)( 2,2';6',2"-terpyridine)]PF6 , 6, (acridine = dibenzo[b,e]pyridine or 2,3-benzoquinoline) that was obtained from the reaction between [Ru(3-acridine-2′-C5H4N-$K$C,N) (MeCN) 4 ]PF6 , 4, and terpy in MeOH/MeCN at 60°C during 24 hours. Likewise to 2, the isomerization of 6 to [Ru(3-acridine-2′-C5H4 N-$K$C,N)(MeCN-trans-C) (terpy)]PF6 , 7, could be induced thermally (48 h at 60 °C in pure MeOH) or photochemically under UV radiations in MeCN at room temperature. A compound closely related to 7 but in which MeCN was replaced by H2O, was described earlier (Tanaka et al. Inorg. Chem. 2012, 51, 5386-539). The presence of water on this compound had a dramatic effect as far as the coordination of terpy was concerned as its isomerisation to a compound related to 6 (in which H2O instead of MeCN is coordinated to Ru) occurred indeed photochemically via irradiation with visible light.