Diimine Triscarbonyl Re(I) of Isomeric Pyridyl-fulvene Ligands: an Electrochemical, Spectroscopic, and Computational Investigation

Abstract

The synthesis and characterization of a novel family of positively charged fac-[Re(bpy)(CO)(3)(L)]PF(6) (bpy = 2,2'-bipyridine) complexes are reported, where L is a pyridine functionalized in para or meta position with a fulvene moiety, namely, 4-fluoren-9-ylidenemethyl-pyridine (pFpy) and 3-fluoren-9-ylidenemethyl-pyridine (mFpy). The complexes were prepared in high yield (86%) by direct addition at room temperature of the corresponding pyridine to the tetrahydrofuran (THF) adduct fac-[Re(bpy)(CO)(3)(THF)][PF(6)] precursor. Both ligand and complex structures were fully characterized by a variety of techniques including X-ray crystallography. The complexes did not exhibit the expected triplet mixed metal-ligand-to-ligand charge transfer (MLLCT) emission, because of its deactivation by the non-emissive triplet excited state of fulvene. The absorption profile shows that the MLLCT is overshadowed by the fulvene centered π-π* transition of higher molar absorptivity as shown by time dependent density functional theory (TD-DFT) calculations. The position of the fulvene on the pyridyl ring has a large effect on this transition, the para position displaying a much higher absorption coefficient (21.3 × 10(3) M(-1) cm(-1)) at lower energy (364 nm) than the meta position (331 nm, 16.0 × 10(3) M(-1) cm(-1)).

Gold(I) Complexes of Fulvenyl‐Functionalized Arylisocyanides

“…However, preparation of complexes suitable for metal-to-ligand charge transfer {MLCT, e.g. Cr 0 , [4a] W 0 , [4a] Re I [14] }, or ligand-to-metal charge transfer {LMCT, e.g. Pt I , Pd I [23] } would give rise to compounds with intriguing electronic and optical properties, since the electron accepting and releasing properties of the ligands can be tailored through choice of the fulvenyl substituent.…”

“…In these prior cases the electronic effect of the fulvene on the electronic properties of the complexes had not been the main focus of the work. Contrarily, Hanan and co‐workers devised fluorene‐based pyridyl‐fulvene‐ligands, and studied the optical properties and intramolecular charge‐transfer processes in the corresponding rhenium carbonyl complexes ( 4a and 4b ) . In our group, we also take an interest in harnessing the properties of fulvenes to prepare electroactive materials with tailored electrochemical and optical properties.…”

“…Contrarily, Hanan and co-workers devised fluorene-based pyridylfulvene-ligands, and studied the optical properties and intramolecular charge-transfer processes in the corresponding rhenium carbonyl complexes (4a and 4b). [14] In our group, we also take an interest in harnessing the properties of fulvenes to prepare electroactive materials with tailored electrochemical and optical properties. To this end, we have recently published the synthesis of the fulvenyl-functionalized isocyanides L1-L3 (Scheme 3), and the corresponding poly(isocyanide)s along with studies of their electrochemical and optical properties.…”

Photochemical properties of a Re(I) polymer containing dppz in its structure. An interplay between dark and bright states of dppz

“…LLCT and IL transitions [18][19][20][21][22][23][24][25][26][27]. The electronic structure of the Re(I) tricarbonyl complex were determined using tools of DFT [28][29][30] as implemented in Gaussian 09 package [31].…”

Manganese, technetium and rhenium

“…79 The mechanism of photoisomerisation of stilbene-like ligands coordinated to rhenium(I) carbonyl complexes has been determined and reported, 80 while the effect of structural variations in substituted pyridine ligands on the spectroscopic and electrochemical characteristics of diimine tricarbonyl rhenium(I) complexes has also been investigated. 81 The photoredox and photophysical characteristics of a novel tricarbonyl rhenium(I) complex bearing a (dimesityl)boryldurylethynyl group at the 4-position of a 1,10-phenanthroline ligand have been disclosed. 82 Meanwhile, two more novel rhenium(I) tricarbonyl diimine complexes have been prepared and their photochemistry with 4-cyanophenol in acetonitrile solution explored.…”