4.7 Article

In-Depth Studies of Ground- and Excited-State Properties of Re(I) Carbonyl Complexes Bearing 2,2′:6′,2-Terpyridine and 2,6-Bis(pyrazin-2-yl)pyridine Coupled with π-Conjugated Aryl Chromophores

Journal

INORGANIC CHEMISTRY
Volume 60, Issue 24, Pages 18726-18738

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acs.inorgchem.1c02151

Keywords

-

Funding

  1. National Science Centre of Poland [DEC-2017/25/B/ST5/01611]
  2. Wroclaw Centre for Networking and Supercomputing [18]
  3. PIK-Programme for new interdisciplinary elements of education at the doctoral level for the field of chemistry [POWR.03.02.00-00-I010/17]

Ask authors/readers for more resources

In this study, eight rhenium(I) complexes incorporating 2,2':6',2''-terpyridine (terpy) and 2,6-bis(pyrazin-2-yl)pyridine (dppy) with appended 1-naphthyl-, 2-naphthyl-, 9-phenanthrenyl, and 1-pyrenyl groups were comprehensively studied. The presence of naphthyl and phenanthrenyl substituents did not significantly affect the energy of the MLCT absorption and emission bands, while the addition of the electron-rich pyrenyl group resulted in a noticeable red shift and increased molar absorption coefficients of the lowest energy absorption. The excited states of complexes with 1-pyrenyl-functionalized ligands were found to exhibit predominant characteristics of (ILpyrene)-I-3/(ILCTpyrene -> terpy)-I-3 at 77 K.
In the current work, comprehensive photophysical and electrochemical studies were performed for eight rhenium(I) complexes incorporating 2,2':6',2 ''-terpyridine (terpy) and 2,6-bis(pyrazin-2-yl)pyridine (dppy) with appended 1-naphthyl-, 2-naphthyl-, 9-phenanthrenyl, and 1-pyrenyl groups. Naphthyl and phenanthrenyl substituents marginally affected the energy of the MLCT absorption and emission bands, signaling a weak electronic coupling of the appended aryl group with the Re(I) center. The triplet MLCT state in these complexes is so low lying relative to the triplet (ILaryl)-I-3 that the thermal population of the triplet excited state delocalized on the organic chromophore is ineffective. The attachment of the electron-rich pyrenyl group resulted in a noticeable red shift and a significant increase in molar absorption coefficients of the lowest energy absorption of the resulting Re(I) complexes due to the contribution of intraligand charge-transfer (ILCT) transitions occurring from the pyrenyl substituent to the terpy/dppy core. At 77 K, the excited states of [ReCl(CO)(3)(L-n-kappa N-2)] with 1-pyrenyl-functionalized ligands were found to have predominant (ILpyrene)-I-3/(ILCTpyrene -> terpy)-I-3 character. The (IL)-I-3/(ILCT)-I-3 nature of the lowest energy excited state of [ReCl(CO)(3)(4'-(1-pyrenyl)-terpy-kappa N-2)] was also evidenced by nanosecond transient absorption and time-resolved emission spectroscopy. Enhanced room-temperature emission lifetimes of the complexes [ReCl(CO)(3)(L-n-kappa N-2)] with 1-pyrenyl-substituted ligands are indicative of the thermal activation between (MLCT)-M-3 and (IL)-I-3/(ILCT)-I-3 excited states. Deactivation pathways occurring upon light excitation in [ReCl(CO)(3)(4'-(1-naphthyl)-terpy-kappa N-2)] and [ReCl(CO)(3)(4'-(1-pyrenyl)-terpy-kappa N-2)] were determined by femtosecond transient absorption studies.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.7
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available