Spectral-luminescence properties of a norbornene-substituted tetraazachlorin and its metal complexes

Abstract

The spectral-luminescence properties of a tetraazachlorin derivative with a norbornene fragment annelated to a reduced pyrrole ring and its complexes with zinc and palladium have been studied at 293 and 77 K. For the norbornene-substituted free base, differences in fluorescence from unsubstituted tetraazachlroin and its dibenzobarrelene-substituted analog are found. The fluorescence lifetime is observed to rise by ~7 times for the free base and by ~1.6 ties for the Zn complex on going from 293 to 77 K. An essential dependence of the photophysical parameters on the nature of the solvent is noted. The fluorescence polarization spectrum of the norbornene-substituted tetraazachlorin reveals in the Soret band region at least four electronic transitions. For the Pd complex, weak phosphorescence in the near IR region has been detected; the 0-0 band maximum is at 990 nm and the singlet-triplet interval amounts to 5800 cm -1 , which is larger by 400 cm -1 than for Pd tetraazaporphine. The quantum yields of the photosensitized formation of singlet oxygen have been determined using a relative luminescence method.

Spectral and Luminescent Characteristics of a Hexaphenyltetraazachlorin Zinc Complex

“…Analogous spectra for norbornene-substituted zinc tetraazachlorin (ZnTAC nb ) are shown in Fig. 1c for comparison [5]. It is noteworthy that substitution in the hydrogenated ring (like in this instance) had almost no effect on the electronic spectra of the tetraazachlorins [3,5,7].…”

“…These were tetramethylhexaphenyltetraazachlorin [2] (H 2 Ph 6 TAC tm , where tm = tetramethyl) and N-methylpyrrolidineoctaphenyltetraazachlorin, the spectral properties of which differed slightly. The zinc complexes were studied in parallel with the free bases in a series of studies [3][4][5] in order to expand information on the properties of the macrocycles. Therefore, it seemed advisable to continue the work [1] by studying the photophysical characteristics of the zinc complex ZnPh 6 TAC tm :…”

Phosphorescence of palladium and platinum complexes of benzo-fused hydroporphyrazines

“…Benzosubstitution in the presence of nitrogen bridges decreases ΔE ST by ~400 cm -1 according to data for ZnTAP [35], PdTAP [34], and Zn-and PdPc [14]. Finally, phosphorescence of Pd-norbornenotetraazachlorin was recently recorded [6]. The ΔE ST value was 5800 cm -1 .…”

“…It is noteworthy that the spectral and luminescence properties of metal-free arenotetraazachlorins were studied [5], including stable spectral hole burning in the absorption spectra. Phosphorescence of a Pd complex of a substituted tetraazachlorin was recorded in other work [6] where references are given to all other publications of our group on the spectroscopy and photophysics of hydroporphyrazines. …”

“…Solvent for MBPpa, Et2O[37]; MTBTAC, MDBTABC, and NiDBTAiBC, chlorobenzene (Ni complexes[3]); Pd-and PtDBTAiBC, hexane; H2-and PdTAC nb , MTHF[6]; Ni-and ZnTAC nb , Py (our own data); MOEC (T = 77 K), EPIP mixture [Et2O:petroleum ether:isopropanol (5:5:2)]; MgOEC, petroleum ether[29]; MOAlkP, Py (Mg), benzene (Cu, Zn)[38], Et2O:isopentane:EtOH (5:5:2) with added DMF (Ni, Pd, Pt)[18]; H2OEP, benzene[38]. Slight justified changes were made to the tabular data[29].…”