Linker Conjugation Effects in Rhenium(I) Bifunctional Hole‐Transport/Emitter Molecules

Abstract

Spectroscopic, electrochemical and density functional theory (DFT) methods have been employed to investigate a group of [Re(CO)(3)(HT)(phen)](+) complexes (phen = 1,10-phenanthroline), and in particular the level of electronic communication between various hole-transporting (HT) ligands and the rhenium centre. Here, the HT ligand consists of a coordinating pyridine connected to dimethylaniline group through a single-, double- or triple-bond-connecting system. Electronic absorption, resonance Raman, and steady-state emission spectroscopy combined with lifetime studies and DFT calculations suggest that multiple dpi(Re)-->pi*(phen) metal-to-ligand charge transfers (MLCTs) exist for each complex, two of which significantly absorb at about 340 and 385 nm, and one that emits at approximately 540 nm. In the complexes containing more-conjugated HT ligands, non-emissive intraligand transitions (IL(HT)) exist with energies between the ground and MLCT excited states. The overlap of these IL(HT) transitions and the absorbing MLCT of lowest energy deactivates emission resulting from about 385 nm excitation, and lowers the quantum yield and excited-state lifetimes of these complexes. Cyclic voltammetry experiments indicate that throughout the series investigated, the highest occupied molecular orbital (HOMO) of each complex is centred on the HT ligand, while the occupied molecular orbitals localised on the rhenium are lower in energy.

Photo‐active Cobalt Cubane Model of an Oxygen‐Evolving Catalyst

“…The cobalt-oxo cubane [Co 4 O 4 (CO 2 Py) 2 (bpy) 4 ](ClO 4 ) 2 (1, CO 2 Py = 4-carboxypyridine) was obtained from isonicotinic acid and [Co 4 O 4 (CO 2 Me) 2 (bpy) 4 ](ClO 4 ) 2 by using methods adapted from those reported by Christou [33] (see the Experimental Section and the Supporting Information for synthetic details and full characterisation). Complexation of this functionalised cubane with the rhenium-based photosensitiser [Re(phen)(CO) 3 -(CH 3 CN)]PF 6 [34] (phen = 1,10-phenanthroline) affords a cobaltoxo cubane core ligated by Re I phenanthroline photocentres (2).…”

Relativistic effects in spectroscopy and photophysics of heavy-metal complexes illustrated by spin–orbit calculations of [Re(imidazole)(CO)3(phen)]+

“…It will be demonstrated that the SO model accounts very well for absorption spectra, emission properties, and excited-state dynamics, some of its conclusions being qualitatively different from the spinfree approach. [Re(imH)(CO) 3 (phen)] + represents a broad class of Re I tricarbonyl-diimine complexes [21][22][23], which show very rich photophysics and photochemistry [10,14,15,24] and engage in a range of photonic applications such as photosensitizers and phototriggers of electron-transfer reactions [11,[25][26][27][28][29], photocatalysts of CO 2 reduction [30][31][32], phosphorescent labels and probes of biomolecules [33][34][35][36], sensors [37,38], molecular switches [39][40][41][42] and OLED emitters [43], or probes of ps-ns dynamics of solvents, proteins or supramolecular hosts [11,24,50,51,[63][64][65]. The chosen example [Re(imH)(CO) 3 (phen)] + [44] not only epitomizes the salient features of Re I carbonyl-diimine photophysics but also has a prominent position amongst Re-based photosensitizers because of its ability to trigger photoinduced electron transfer and relaxation dynamics in Re-labeled proteins [11,25,[44]…”

Spectroscopic Studies of Phosphazene Polymers Containing Photoluminescent Metal Complexes

“…The resulting mean absolute deviations (MADs) of the frequencies are shown in Table 4; the values are indicative of satisfactory calculations. [29,[43][44][45][47][48][49][50][51] …”

“…Normal modes that mimic ground-to excited-state geometry changes are preferentially enhanced in intensity and this enables unambiguous assignments to be made of chromophorically active regions in a molecule. [44,47,56,57] respectively, and have therefore been omitted for clarity. The spectrum of [(L 1 -H)PtCl] acquired at 350.7 nm shows resonance-enhancement at 1358, 1483 and around 1610 cm -1 , which are identified as modes delocalised over the entire OPhbpyPh unit with significant contributions from both Ph units.…”