Fe(ii), Ru(ii) and Re(i) complexes of endotopic, sterically non-hindering, U-shaped 8,8′-disubstituted-3,3′-biisoquinoline ligands: syntheses and spectroscopic properties

Abstract

The redox behaviour, optical-absorption spectra and emission properties of U-shaped and elongated disubstituted biisoquinoline ligands and of derived octahedral Fe(ii), Ru(ii), and Re(i) complexes are reported. The ligands are 8,8'-dichloro-3,3'-biisoquinoline (1), 8,8'-dianisyl-3,3'-biisoquinoline (2), and 8,8'-di(phenylanisyl)-3,3'-biisoquinoline (3), and the complexes are [Fe(3)(3)](2+), [Fe(2)(3)](2+), [Ru(1)(phen)(2)](2+), [Ru(2)(3)](2+), [Ru(3)(3)](2+), [Re(2)(py)(CO)(3)](+), and [Re()(py)(CO)(3)](+). For the ligands, the optical properties as observed in dichloromethane are in line with expectations based on the predominant (1)pipi* nature of the involved excited states, with contributions at lower energies from (1)npi* and (1)ILCT (intraligand charge transfer) transitions. For all of the Fe(ii), Ru(ii), and Re(i) complexes, studied in acetonitrile, the transitions associated with the lowest-energy absorption band are of (1)MLCT (metal-to-ligand charge transfer) nature. The emission properties, as observed at room temperature and at 77 K, can be described as follows: (i) the Fe(ii) complexes do not emit, either at room temperature or at 77 K; (ii) the room-temperature emission of the Ru(ii) complexes (phi(em) > 10(-3), tau in the micros range) is of mixed (3)MLCT/(3)LC character (and similarly at 77 K); and (iii) the room-temperature emission of the Re(i) complexes (phi(em) approximately 3 x 10(-3), tau < 1 ns) is of (3)MLCT character and becomes of (3)LC (ligand-centered) character (tau in the ms time scale) at 77 K. The interplay of the involved excited states in determining the luminescence output is examined.

Passing Two Strings through the Same Ring Using an Octahedral Metal Center as Template: A New Synthesis of [3]Rotaxanes

“…In analogy with related complexes previously reported by our group, 22,23,29 this evidence coordination to the metal which favors close proximity between the various organic fragments and thus exposes H 6′ , H 6′′ , and H 1 protons to the strong ringcurrent effects of the aromatic fragments of other ligands.…”

“…22,28 Noteworthy, the MLCT bands of [Fe(bipy) 3 ] 2+ 28 3 2+ and 4 2+ (λ max ) 487 and 523 nm) appear at lower energy than those of 8 2+ and 10 2+ (λ max ) 462 nm) due to the more electron-rich nature of dabiiq compared to that of bipy.…”

The magic effect of endocyclic but non-sterically hindering biisoquinoline chelates: From fast-moving molecular shuttles to [3]rotaxanes

“…In our efforts, we explored both the synthesis of phenyl and biphenyl substituted ligands 1 and 2 [10,11], but encountered serious solubility problems with the latter. However, as anticipated, complexation of these ligands to octahedral metal centres such as Fe(II), Ru(II) and Re(I) proceeds smoothly and with excellent yields [10,12,13]. The homoleptic complexes [Ru II (1) 3 ] 2+ (5 2+ ) and [Fe II (2) 3 ] 2+ (6 2+ ) are particularly interesting: X-ray structure analyses of crystals containing these molecules provide the proof of concept, namely the successful three-component entanglement consisting of three crescent-shaped chelates coordinated to a single octahedral metal centre (Fig.…”

Structure-Guided Evolution of Potent and Selective CHK1 Inhibitors through Scaffold Morphing

“…The lengthy synthesis of 64 has been previously described,(60) while 3-chloroisoquinoline 63 is commercially available and 8-chloroisoquinolin-3-yl trifluoromethanesulfonate 65 was synthesized in large quantities using the method reported by Ventura et al(61)…”