Luminescence of N-Arylbenzamides in Low-Temperature Glasses

Abstract

The low-temperature luminescence of benzamide and six additional N-arylbenzamides has been investigated in a methyltetrahydrofuran glass. The luminescence of microcrystalline benzamide has also been studied. Assignments of the fluorescence and phosphorescence have been made on the basis of comparisons with the spectra of benzamide and the six aminoarenes and with the results of semiempirical ZINDO calculations for the amines and amides. This information was used to construct state-energy diagrams for the six amides. The 430 nm fluorescence of benzanilide and the amides derived from 4-aminobiphenyl and 4-aminodiphenylacetylene is assigned to a n,π* state having a relaxed geometry and localized on the benzoyl group. The structured fluorescence of the amides derived from 4-aminostilbene and 2-aminoanthracene is attributed to a delocalized π,π* singlet state. The amide derived from 2-aminophenanthrene displays dual fluorescence. The amides derived from 4-aminostilbene and 2-aminoanthracene are nonphosphorescent. The structured phosphorescence of the amides derived from the other aminoarenes is assigned to a π,π* triplet state similar to that for the aminoarene. These results serve to further elucidate the unusual luminescence properties of the benzamides in solution as well as in low-temperature glasses.

Luminescent Iridium(III)‐Terpyridine Complexes – Interplay of Ligand Centred and Charge Transfer States

“…in aromatic solvents and at room temperature it displays dual fluorescence which can be assigned to an 1 n-π* transition (λ max = 433 nm) and a twisted intramolecular charge transfer state, 1 TICT (λ max = 510 nm), originating from a relaxed, higher energy 1 π-π* state. [30,31] The extended conjugation at the ligand, which occurs when benzamide units are appended to the tpy fragment coordinated to the metal centre, and the polar solvent could further stabilise the latter state so as to match the detected luminescent level in the present complexes. Accordingly, the low-lying CT transitions detected in the benzamide appended complexes 2 and 3 could be intra-ligand charge transfer in nature ( 3 ILCT) and localised on the N-phenyl benzamide fragment.…”

Pushing the limits of structurally-diverse light-harvesting Ru(II) metal-organic chromophores for photodynamic therapy

“…25 Covalent coupling of known oxygen-independent DNA oxidizing agents through insulating amide bonds may offer an attractive approach for generating novel metal-organic Ru(II) chromophores to treat MG brain cancer through visible light activation. [26][27][28][29] Ru(II) chromophores containing dpp ligands possess the unique added advantage of being able to chelate biologically-relevant cations (i.e. Na + , K + , Ca 2+ , etc.…”

Photochemistry of Oxazolidinone Antibacterial Drugs†

“…Furthermore, such fluorine‐free compounds exhibit both fluorescence in solution and phosphorescence in glass (see Table 4) and resemble anilines in their photophysical properties. Comparison with literature data shows that the fluorescence of parent aniline is at 334 nm ( Φ F = 0.15 in MeCN) and the phosphorescence at 405 nm (in methyltetrahydrofuran glass at 77 K) (33). Thus, the emission from the present derivatives is somewhat redshifted and less intense, but qualitatively of the same type.…”