Issue 21, 2021

Proton-controlled non-exponential photoluminescence in a pyridylamidine-substituted Re(i) complex

Abstract

Chemical intuition and well-known design principles can typically be used to create ligand environments in transition metal complexes to deliberately tune reactivity for desired applications. However, intelligent ligand design does not always result in the expected outcomes. Herein we report the synthesis and characterization of a tricarbonyl rhenium (2,2′-bipyridine) 4-pyridylamidine, Re(4-Pam), complex with unexpected photophysical properties. Photoluminescence kinetics of Re(4-Pam) undergoes non-exponential decay, which can be deconvolved into two emission lifetimes. However, upon protonation of the amidine functionality of the 4-pyridylamidine to form Re(4-PamH), a single exponential decay is observed. To understand and rationalize these experimental observations, density functional theory (DFT) and time-dependent density functional theory (TDDFT) are employed. The symmetry or asymmetry of the protonated or deprotonated 4-pyridylamidine ligand, respectively, is the key factor in switching between one and two photoluminescence lifetimes. Specifically, rotation of the dihedral angle formed between the bipyridine and 4-Pam ligand leads to two rotamers of Re(4-Pam) with degenerate triplet- to ground-state transitions.

Graphical abstract: Proton-controlled non-exponential photoluminescence in a pyridylamidine-substituted Re(i) complex

Supplementary files

Article information

Article type
Paper
Submitted
06 Apr 2021
Accepted
29 Apr 2021
First published
06 May 2021

Dalton Trans., 2021,50, 7265-7276

Author version available

Proton-controlled non-exponential photoluminescence in a pyridylamidine-substituted Re(I) complex

S. M. Martin, A. N. Oldacre, C. A. Pointer, T. Huang, G. M. Repa, L. A. Fredin and E. R. Young, Dalton Trans., 2021, 50, 7265 DOI: 10.1039/D1DT01132D

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