Synthesis and Design of Metalloporphyrin Oligomers with Temperature-Assisted Spectral-Luminescent Properties

Abstract

A number of metal-linked porphyrin oligomers of different structures were synthesized and their luminescent sensitivity to temperature was studied. Density functional theory (DFT) was used to geometrically optimize the resulting compounds structure. Coordination Sn(IV)-dipyridylporphyrin tetramers formed through the interaction of pyridyl fragments of the macrocycle with Pd(II) and Pt(II) cations, as well as the octamer assembled by coordination of pyridyl groups with Pd(II) cations and bis-chelate binding of bidentate ligands in the axial positions of Sn(IV)-porphyrins with the Cu(II) cation, were shown to exhibit fluorescent thermal sensitivity in the temperature range of 328–383 K in the region of 600–650 nm. In this section, the dependence of the fluorescence quantum yield (fluorescence intensity) with a temperature increase is a monotonic pseudolinear trend. The flare-up ranges from 1.5 to 4.5 times, depending on the structure of porphyrin oligomers. At temperatures above 383 K, all studied porphyrin assemblies obtained on the basis of Pd(II) exhibit a decrease in fluorescence intensity. At the same time, their structure is preserved. The porphyrin tetramer obtained from Pt(II) undergoes a structural rearrangement, transforming into a presumably cyclometalated organoplatinum compound that exhibits effective luminescence at 493 nm. The results obtained could be used for the development of new temperature-assisted optoelectronic devices such as sensors, molecular reactors and catalysts.