Bathochromic Shifts in Rhenium Carbonyl Dyes Induced through Destabilization of Occupied Orbitals

Abstract

A series of rhenium diimine carbonyl complexes was prepared and characterized in order to examine the influence of axial ligands on electronic structure. Systematic substitution of the axial carbonyl and acetonitrile ligands of [Re(deeb)(CO)(NCCH)] (deeb = 4,4'-diethylester-2,2'-bipyridine) with trimethylphosphine and chloride, respectively, gives rise to red-shifted absorbance features. These bathochromic shifts result from destabilization of the occupied d-orbitals involved in metal-to-ligand charge-transfer transitions. Time-Dependent Density Functional Theory identified the orbitals involved in each transition and provided support for the changes in orbital energies induced by ligand substitution.

A Rare Type of Rhenium(I) Diimine Complexes with Unsupported Coordinated Phosphine Oxide Ligands: Synthesis, Structural Characterization, Photophysical and Theoretical Study

“…In dichloromethane solution all compounds display yellow to orange 3 MLCT [π*(N–N)→dπ(Re)] phosphorescence with structureless emission bands (Figure ) and lifetimes in the range 0.5–0.7 µs in degassed solution (Table ). The assignment of the phosphorescence to 3 MLCT (where M implies rhenium tricarbonyl motif) excited state is also supported by DFT calculations (Figure , Figure S14, Table S6) and is in complete agreement with the experimental results and theoretical analysis of closely analogous systems studied earlier . It is also well‐known, that insertion of electron‐donating substituents into coordinated diimine ligand leds to a hypsochromic shift of the emission maximum, and this trend is clearly observed for the complexes under study.…”

“…10 nm due to stabilization of the metal orbitals because of lower overall donicity of the latter phosphine oxide ligand. Comparative analysis of key photophysical characteristics of the complex 1Re (OPPh 3 ) and the [Re(CO) 3 (neocuproine)L] compounds {L = PPh 3 [ 1Re(PPh 3 ) ], NCMe [ 1Re(NCMe) ], Cl – [ 1Re(Cl) ]} shows the representative correlation with the σ/π‐donor/acceptor properties of the axial ligand . The σ/π‐donation by the Cl – ligand destabilizes metal ion localized HOMO and red‐shifts the low energy absorbance and emission bands in the selected series of complexes (Figure , Figure S10, Table ).…”

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

“…In the later studies two other synthetic approaches were used to selectively substitute CO (Scheme 1): photochemical Re-CO bond braking under steady-state UV irradiation [29][30][31][32][33][34][35][36][37][38] and selective decarbonylation with trimethylamine-N-oxide (TMANO). [39][40][41] These approaches make possible to synthesize different types of polynuclear species with potential application in different areas such as light-emitting devices and lightharvesting antennae. [37,42] In both approaches the presence of the heteroligand with strong labilizing trans-effect (L = PR 3 , C � N À ) facilitate CO substitution in trans-position to L. In the case of the ligands with low trans-effect (L = NCMe, Py, Cl) it is possible to obtain Re(N N)(CO) 2 (L)(L') compounds utilizing photochemical substitution under high energy irradiation (313 nm), but this reaction affords a mixture of isomeric products.…”

“…This means that fine tuning of the absorption and emission characteristics can be done either through the modification of the diimine ligand properties (insertion of donor/acceptor substituents and expansion of the aromatic system [44,45] ) or by manipulation with the energy of metal orbitals using heteroligands with essentially different donor/ acceptor abilities. [41] It is worth noting that in general the rhenium complexes mentioned above typically display low absorption across the visible spectrum and luminesce in the green-yellow spectral area that stems from rather large energy gap in MLCT transitions and makes it difficult to use these emitters in photocatalytic and biomedical applications. Red shift of absorption/excitation and emission bands may be achieved by the stabilization of the ligand π*-orbitals with electron withdrawing substituents, [46] but the effect can be substantially enhanced by a targeted variations in the properties of the heteroligands, which may increase the energy of metal orbitals with the increase in their donor ability, see for example Figure 1.…”

Influence of the Nucleophilic Ligand on the Reactivity of Carbonyl Rhenium(I) Complexes towards Methyl Propiolate: A Computational Chemistry Perspective

“…Therefore, to get more general conclusions about these processes, ultimately aiming at tuning the Re complexes in order to obtain more interesting synthetic, industrial or biochemical applications [ 59 , 60 ], a more systematic computational investigation is needed. To accomplish this task, we undertook a theoretical study on the reaction mechanism of the reactivity towards the substrate HMAD of the complexes [ReY(CO) 3 (bipy)] (Y = NH 2 , NHMe, OPh, PH 2 , PHMe, PMe 2 , PHPh, PMePh, SH, SMe, SPh).…”