scholarly journals The Effect of N-Heterocyclic Carbene Units on the Absorption Spectra of Fe(II) Complexes: A Challenge for Theory

2020 ◽  
Author(s):  
Olga S. Bokareva ◽  
Omar Baig ◽  
Mohamed Al-Marri ◽  
Oliver Kühn ◽  
Leticia Gonzalez
Keyword(s):  
Charge Transfer ◽  
Absorption Spectra ◽  
Excited States ◽  
Partial Charge Transfer ◽  
Polypyridyl Ligands ◽  
Electronic Excited States ◽  
Heteroleptic Complexes ◽  
Ligand Charge Transfer ◽  
Exact Exchange ◽  
Triplet Excited States

<div>The absorption spectra of five Fe(II) homoleptic and heteroleptic complexes containing strong sigma-donating N-heterocyclic carbene (NHC) and polypyridyl ligands have been theoretically characterized using a tuned range-separation functional.</div><div>From a benchmark comparison of the obtained results against other functionals and a multiconfigurational reference, it is concluded that none of the methods is completely satisfactory to describe the absorption spectra.</div><div>Using a compromised choice of 20\% exact exchange, the electronic excited states underlying the absorption spectra are analyzed.</div><div>The low-lying energy band of all the compounds shows predominant metal-to-ligand charge transfer (MLCT) character while the triplet excited states have metal-centered (MC) nature, which becomes more pronounced with increasing the number of NHC-donor groups. Excited MC states with partial charge transfer to the NHC-donor groups are higher in energy than comparable states without these contributions. The presence of the low-lying MC states prevents the formation of long-lived MLCT states.</div>

scholarly journals The Effect of N-Heterocyclic Carbene Units on the Absorption Spectra of Fe(II) Complexes: A Challenge for Theory

2020 ◽  
Author(s):  
Olga S. Bokareva ◽  
Omar Baig ◽  
Mohamed Al-Marri ◽  
Oliver Kühn ◽  
Leticia Gonzalez
Keyword(s):  
Charge Transfer ◽  
Absorption Spectra ◽  
Excited States ◽  
Partial Charge Transfer ◽  
Polypyridyl Ligands ◽  
Electronic Excited States ◽  
Heteroleptic Complexes ◽  
Ligand Charge Transfer ◽  
Exact Exchange ◽  
Triplet Excited States

<div>The absorption spectra of five Fe(II) homoleptic and heteroleptic complexes containing strong sigma-donating N-heterocyclic carbene (NHC) and polypyridyl ligands have been theoretically characterized using a tuned range-separation functional.</div><div>From a benchmark comparison of the obtained results against other functionals and a multiconfigurational reference, it is concluded that none of the methods is completely satisfactory to describe the absorption spectra.</div><div>Using a compromised choice of 20\% exact exchange, the electronic excited states underlying the absorption spectra are analyzed.</div><div>The low-lying energy band of all the compounds shows predominant metal-to-ligand charge transfer (MLCT) character while the triplet excited states have metal-centered (MC) nature, which becomes more pronounced with increasing the number of NHC-donor groups. Excited MC states with partial charge transfer to the NHC-donor groups are higher in energy than comparable states without these contributions. The presence of the low-lying MC states prevents the formation of long-lived MLCT states.</div>

Synthesis and Photochemical Properties of Re(I) Tricarbonyl Complexes Bound to Thione and Thiazole-2-ylidene Ligands

2020 ◽  
Author(s):  
Matthew Stout ◽  
Brian Skelton ◽  
Alexandre N. Sobolev ◽  
Paolo Raiteri ◽  
Massimiliano Massi ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Ligand Exchange ◽  
Ligand Substitution ◽  
Bidentate Ligand ◽  
The Other ◽  
Ligand Exchange Reaction ◽  
Multiple Products ◽  
Ligand Charge Transfer ◽  
Photochemical Properties

<p>Three Re(I) tricarbonyl complexes, with general formulation Re(N^L)(CO)<sub>3</sub>X (where N^L is a bidentate ligand containing a pyridine functionalized in the position 2 with a thione or a thiazol-2-ylidene group and X is either chloro or bromo) were synthesized and their reactivity explored in terms of solvent-dependent ligand substitution, both in the ground and excited states. When dissolved in acetonitrile, the complexes bound to the thione ligand underwent ligand exchange with the solvent resulting in the formation of Re(NCMe)<sub>2</sub>(CO)<sub>3</sub>X. The exchange was found to be reversible, and the starting complex was reformed upon removal of the solvent. On the other hand, the complexes appeared inert in dichloromethane or acetone. Conversely, the complex bound to the thiazole-2-ylidene ligand did not display any ligand exchange reaction in the dark, but underwent photoactivated ligand substitution when excited to its lowest metal-to-ligand charge transfer manifold. Photolysis of this complex in acetonitrile generated multiple products, including Re(I) tricarbonyl and dicarbonyl solvato-complexes as well as free thiazole-2-ylidene ligand.</p>

scholarly journals Rational Design of TADF Polymers Using a Donor-Acceptor Monomer with Enhanced TADF Efficiency Induced by the Energy Alignment of Charge Transfer and Local Triplet Excited States

2016 ◽  
Vol 4 (4) ◽  
pp. 597-607 ◽  
Author(s):  
Roberto S. Nobuyasu ◽  
Zhongjie Ren ◽  
Gareth C. Griffiths ◽  
Andrei S. Batsanov ◽  
Przemyslaw Data ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Rational Design ◽  
Donor Acceptor ◽  
Triplet Excited States

scholarly journals Cation Sensing Capabilities of A Nitrophenyl Cinnamaldehyde Derivative

Molekul ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 191
Author(s):  
Venty Suryanti ◽  
Fajar Rakhman Wibowo ◽  
Ahmad Marzuki ◽  
Meiyanti Ratna Kumala Sari
Keyword(s):  
Charge Transfer ◽  
Organic Compound ◽  
Charge Density ◽  
Absorption Spectra ◽  
Color Change ◽  
Metal Cations ◽  
Colorimetric Sensing ◽  
Color Changes ◽  
Ligand Charge Transfer ◽  
Cation Sensing

The cationic chemosensor based on organic compound bearing an aminophenol moiety as a receptor for metal analyte and a cinnamaldehyde moiety as chromophoric fragment has been developed. In this work, we report the colorimetric sensing of nitrophenyl cinnamaldehyde derivative, namely methyl-3-(2-hidroxy-5-nitrophenyl amino)-3-phenylpropanoate, towards a variety of metal cations, such as Cu2+, Fe3+, Ni2+ and Zn2+. The cation sensing abilities of the sensor were observed for Cu2+and Fe3+ with a color change from colorless to pink and faint yellow, respectively, The characteristic UV-Vis spectra changes were observed upon addition of Cu2+and Fe3+ cations. The hypsochromic absorption spectra shifts were obtained, indicating the cations and sensor complexations had formed. A metal-to-ligand-charge-transfer (MLCT) had occurred and the charge density of the sensor changed resulting in appearance of new absorption peaks in the UV-Vis spectra and color changes of the sensor solution upon addition of the Cu2+and Fe3+.  

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