Trinuclear Copper(I) Complex Containing 3,4,9,10,15,16-Hexamethyl-1,6,7,12,13,18-hexaazatrinaphthylene: A Structural, Spectroscopic, and Computational Study

Abstract

The compound [(Cu(PPh(3))(2))(3)(HATNMe(6))](BF(4))(3) has been synthesized and characterized by X-ray crystallography, resonance Raman spectroscopy, and density functional theory (DFT) calculations. The X-ray structure of solvated [(Cu(PPh(3))(2))(3)(HATNMe(6))](BF(4))(3) [rhombohedral, R3, a = b = 21.6404(4) A, c = 53.188(3) A, alpha = beta = 90 degrees, gamma = 120 degrees] shows that the HATNMe(6) ligand is very slightly twisted. The electronic absorption spectrum of the complex in chloroform shows two bands in the visible region attributed to ligand-centered (LC) and metal-to-ligand charge-transfer (MLCT) transitions, respectively. Time-dependent DFT calculations show good agreement with experiment, with two MLCT and one LC transition predicted in the visible region (641, 540, and 500 nm). Resonance Raman spectra of the complex using discrete excitation energies between 647 and 406 nm showed a variation in enhancement patterns consistent with at least two distinct transitions. The absolute Raman cross sections have been evaluated and, through a wavepacket analysis, the amount of distortion along each vibrational mode across the Franck-Condon surface is established from the calculated dimensionless displacement (Delta) values as well as other electronic parameters. The pattern of Delta values shows good agreement with the observed calculated modes, with the MLCT transition, showing much larger Delta values for outer ring modes such as nu(93) and nu(205) than in the LC transition. This is consistent with the molecular orbitals involved in the two transitions; the donor orbitals for the LC transition have similar outer-ring bonding characteristics compared to the MLCT transition, which has no donor orbital bonding characteristics on the ligand because the donor molecular orbitals are dpi orbitals.

Walking the Emission Tightrope: Spectral and Computational Analysis of Some Dual-Emitting Benzothiadiazole Donor–Acceptor Dyes

“…Resonance Raman data and eigenvector diagrams for BTD-TPA are shown in Figure while the remaining spectra are shown in Figure S7. Resonance Raman spectroscopy is an effective tool for identifying active chromophores as a result of region specific band enhancement that occurs coincident with ground → excited state distortions. − When band resonance enhancement is monitored as a function of excitation wavelength, the nature of transitions can be probed. For this series of compounds, emission precludes data collection to the red of 448–491 nm, depending on the compound.…”

When “Donor–Acceptor” Dyes Delocalize: A Spectroscopic and Computational Study of D–A Dyes Using “Michler’s Base”

“…Resonance Raman spectra at a number of excitation wavelengths are presented in Figures and S7 and S8. Resonance Raman spectroscopy can be used to identify active chromophores within a molecule, as characteristic enhancement profiles occur for modes that are coincident with Δ q distortions between the ground and excited states. − The absorption profile is scanned for each compound, and through monitoring of band enhancement, the nature of the transitions is probed. In most cases, data was captured close to the lowest energy λ max .…”

Stretching the phenazine MO in dppz: the effect of phenyl and phenyl–ethynyl groups on the photophysics of Re(i) dppz complexes

“…Resonance Raman spectra were recorded using a previously described setup. [22][23][24][25] Excitation wavelengths 351, 406 and 413 nm were provided by a krypton ion laser (Coherent Inc.); 448 nm was provided by a crystal diode laser (CrystaLaser). Concentrations were typically 1 mM in CH 2 Cl 2 .…”