Effect of Sulfur-Based Substituents on the Electronic Properties of Re(I) dppz Complexes

Abstract

A series of sulfur-substituted dppz-based ligands and their Re(I)(CO)(3)Cl complexes are reported. The sulfur-substituted ligands and complexes show interesting electronic properties atypical of dppz-type systems. Substitution of dppz with thiocyanate (SCN) groups results in behavior typical of an electron withdrawing group. However, substitution of dppz with the electron donating trithiocarbonate (S(2)CS) or deca-alkylthioether (Sdec) groups confer intraligand charge-transfer (ICT) from the S adduct to the phenazine lowest unoccupied molecular orbital (LUMO). Upon complexation of the substituted dppz ligand to Re(CO)(3)Cl this ICT red-shifts and increases in intensity. Analysis of these observations using density functional theory (DFT) calculations and resonance Raman spectroscopy reveals that these transitions are a mixture of metal-to-ligand charge-transfer (MLCT) and S --> phenazine ICT in nature. The synthesized compounds are also characterized using (1)H NMR spectroscopy, IR spectroscopy, and electrochemistry. Single-crystal X-ray analysis was performed on dppz(SCN)(2) (C(20)H(18)N(6)S(2) a = 8.780 A, b = 9.792 A, c = 10.400 A, alpha = 95.95 degrees , beta = 112.13 degrees , gamma = 95.38 degrees , triclinic, P1, Z = 2, R1 = 0.0306, wR2 = 0.0829.

Dinuclear rhenium(I) carbonyl complexes based on π-conjugated polypyridyl ligands with tetrathiafulvalenes: Syntheses, crystal structures, properties and DFT calculations

“…More recently, rhenium(I) complexes containing sulfur-substituted dppz-based ligands have been studied by Gordon et al, which are promising metal-ion-based molecular probes for DNA because of unique emission properties arising from extended dppz moiety [16]. In this paper, 2,3-di(2-pyridyl)quinoxaline (dpq) as the polypyridyl ligand is attached to the TTF unit and a series of TTF-dpq bridging ligands L 1 ÀL 3 with extended p systems have been prepared (Scheme 1).…”

Computational investigations of click-derived 1,2,3-triazoles as keystone ligands for complexation with transition metals: a review

“…It should be mentioned that Raman spectroscopy can probe the nature of electronic transitions and also provide an insight into the structural character of the donor and acceptor MOs. 46 Clearly speaking, the resonance effect enhances the Raman spectra bands corresponding to the structural changes associated with the photoexcitation. [47][48][49][50][51][52] So, the pattern of band enhancements can be combined and interpreted with a computational analysis of the vibration normal modes.…”

Luminescent sensor for copper(II) ion based on imine functionalized monometallic rhenium(I) complexes

“…S16 in supporting information. It can be noted that the experimental and calculated spectra are in good agreement, except that the lowest energy transition in the calculated spectra is shifted to longer wavelength compared to the experimental spectra [51]. The shift towards longer wavelength in calculated spectra is because the B3LYP functional underestimates the energies of MLCT and related charge transfer transitions.…”

“…DFT calculations were performed using G09 package [50] and visualized using 6-31G(d) basis set was used for ligands, whereas LANL2DZ basis set was used to describe Re(I) metal center [51]. The output frequencies were scaled by a factor of approximately 0.975 to minimize mean actual deviation (MAD) between the experimental and the calculated spectra [52].…”