Syntheses and Photophysical Properties of N‐Pyridylimidazol‐2‐ylidene Tetracyanoruthenates(II) and Photochromic Studies of Their Dithienylethene‐Containing Derivatives

Abstract

A series of tetracyanoruthenate(II) with chelating pyridyl N-heterocyclic carbene ligands (NHC-py) was synthesized and characterized. Their photophysical and electrochemical properties as well as the photochromic behavior of their dithienylethene-containing complexes were studied. Photocyclization was found to take place upon irradiation into the metal-to-ligand charge transfer (MLCT) absorption bands of these complexes, and evidence is provided to support the triplet-sensitizing reaction pathway.

N-heterocyclic carbene metal complexes: photoluminescence and applications

“…5). 24 The energy absorption bands of complexes 8 and 9 were assigned mainly to intraligand (IL) transitions with some mixing of a p(im)p*(py) intraligand charge transfer (ILCT) transition. A substantial change was observed for the low-energy band by the addition of acid to methanolic solutions.…”

Photochromic Transitional Metal Complexes for Photosensitization

“…Importantly, the absorptions of the closed forms in the rhenium(I) complexes were found to be significantly red-shifted compared to those of their free ligands (710 nm vs 580 nm) (Figure 2.15b). This was attributed to the more extensive -conjugation due to the metal-assisted planarization of the 2-pyridylimidazole moiety and the perturbation of the metal center [41]. Such effects have also been observed when these ligands were incorporated into the dialkynylplatinum(II) complexes [42].…”

“…However, it could not be sensitized by the 3 LL ′ CT excited state of the bis(thiolate)zinc(II) complexes [39]. Subsequently, similar design of the diarylethene-containing diimine (L8-L9) and pyridyl N-heterocyclic carbene (L10-L12) ligands based on the 2-pyridylimidazoles has also been reported [40,41]. Similar to L7, the photocyclization of L8-L9 in the tricarbonylrhenium(I) complexes and L10-L12 in the tetracyanoruthenate(II) complexes could be photosensitized with the 3 MLCT excited state of the complexes (Figure 2.15a) [41,42].…”

“…Subsequently, similar design of the diarylethene-containing diimine (L8-L9) and pyridyl N-heterocyclic carbene (L10-L12) ligands based on the 2-pyridylimidazoles has also been reported [40,41]. Similar to L7, the photocyclization of L8-L9 in the tricarbonylrhenium(I) complexes and L10-L12 in the tetracyanoruthenate(II) complexes could be photosensitized with the 3 MLCT excited state of the complexes (Figure 2.15a) [41,42]. Importantly, the absorptions of the closed forms in the rhenium(I) complexes were found to be significantly red-shifted compared to those of their free ligands (710 nm vs 580 nm) (Figure 2.15b).…”

Iridium(iii) N-heterocyclic carbene complexes: an experimental and theoretical study of structural, spectroscopic, electrochemical and electrogenerated chemiluminescence properties

“…Providing a versatile synthetic framework and fine control of electronic properties, N-heterocyclic carbenes (NHC) are emerging as a useful option for the development of novel luminescent materials. [1][2][3][4] In recent years, luminescent complexes of metals such as Cu(I), 5,6 Ag(I), 7,8 Au(I), 7,[9][10][11][12] Ni(II), 13 Pd(II), 13,14 Pt(II), [13][14][15][16][17] Ir(III), [18][19][20][21] Ru(II), [22][23][24][25][26][27] Os(II), 28 Re(I), 29,30 Zr(IV), 31 and Hf(IV), 31 incorporating NHC ligands have been devised for a wide range of fundamental investigations, photoluminescence applications and light-emitting devices. Similarly, NHC ligands have recently been exploited to manipulate the electrochemical and spectroscopic properties of metal complexes for electrogenerated chemiluminescence (also known as electrochemiluminescence or ECL).…”