Luminescent Rhenium(I) Phenanthroline Complexes with a Benzoxazol-2-ylidene Ligand: Synthesis, Characterization, and Photophysical Study

Abstract

A series of luminescent rhenium­(I) phenanthroline complexes containing benzoxazol-2-ylidene ligands with the general formula {Re­(CO)3(phen)­[CN­(X)­C6H4-2-O]}+ and cis,trans-{Re­(CO)2(phen)­(L)­[CN­(H)­C6H4-2-O]}+ (X = H, methyl; phen = 1,10-phenanthroline; L = PPh3, PPh2Me, P­(OEt)3) have been synthesized and characterized. The X-ray crystal structures of most of the carbene complexes and some of their synthetic precursors have also been determined. A new synthetic methodology for the preparation of dicarbonyl rhenium diimine synthetic precursors with a labile acetonitrile ligand, [Re­(CO)2(phen)­(PR3)­(MeCN)]+, was developed. Photophysical study shows that these carbene complexes display a green to red 3MLLCT [dπ­(Re) → π*­(N–N)] phosphorescence at room temperature. The N-deprotonations of the benzoxazol-2-ylidene ligand in these complexes were investigated.

Cationic rhenium complexes ligated with N-heterocyclic carbenes – an overview

“…Dalton Transactions taining rhenium carbonyl complexes (37, 42x). 28 As previously reported, N,O-heterogenocarbene complexes can be built via intramolecular cyclization, if the isocyanide C atom is not deactivated by strong (d → p)π-back-bonding from the metal core. 1i,29 Contrary to similar rhenium complexes published by Hahn et al, 29a the strong π-accepting carbonyl ligands coordinated to the rhenium precursor support the formation of the reported luminescent rhenium complexes 38, 39 and 43a-c (Scheme 11).…”

“…Similar reactions with several phosphines bearing rhenium phenanthroline precursors 41x lead to carbene complexes 43x where both carbonyl ligands are arranged in the cis conformation (Scheme 12). 28 Furthermore, the same group reported based on their previous work 28in 2014 luminescent N,S-, N,N-, and N,O-NHC rhenium(I) complexes via a ligand substitution reaction. 13b Starting from Re(CO) 5 Br (16) via a neutral bis(N,O-carbene) rhenium precursor 44 several cationic mono carbene rhenium compounds (45x, 46), could be obtained.…”

Targeted Synthesis of NIR Luminescent Rhenium Diimine cis,trans‐[Re()(CO)2(L)2]n+ Complexes Containing N‐Donor Axial Ligands: Photophysical, Electrochemical, and Theoretical Studies

“…The ReÀ N(acetonitrile) bond lengths fall in the range 2.061-2.076 Å that is considerably shorter than the distances found in the complexes containing acetonitrile coordinated in trans-position relative to the strong field ligands (carbonyl and phosphines) where bonding distances are normally in the range of 2.10-2.16 Å. [47,48] The composition and structure of the acetonitrile derivatives in solution were investigated by using massspectrometry and NMR spectroscopy. The ESI + mass spectra display the major signal of singly charged cations with the m/z values and isotopic patterns corresponding to the stoichiometry of the molecular ions [(N N)Re(NCMe) 2 ] + ( Figure S1-S2 Figures S5-S6).…”

Potential theranostic and multimodal iron oxide nanoparticles decorated with rhenium–bipyridine and –phenanthroline complexes

“…Rhenium(I) in combination with 1,10-phenanthroline or 2,2 0 -bipyridine is known to render an excellent antenna and luminescence in the orange (590-620 nm) region of the electromagnetic spectrum. [41][42][43] A covalent attachment is formed on the surface of the iron oxide nanoparticles due to the high affinity of rhenium(I) towards pyridine ligands. Via this approach the iron oxide nanoparticles are kept small, so as to profit from T 1 and T 2 contributions for MRI purposes [10][11][12] and a rhenium antenna structure serves as a probe for optical imaging.…”