A spectroscopic investigation of luminescent Cr(III) complexes

Sawicka, Natalia 2023. A spectroscopic investigation of luminescent Cr(III) complexes. PhD Thesis, Cardiff University. Item availability restricted.

Preview	PDF - Accepted Post-Print Version Download (10MB) | Preview
	PDF (Cardiff University Electronic Publication Form) - Supplemental Material Restricted to Repository staff only Download (120kB)

Abstract

Long-lived luminescent compounds are desirable for a range of optoelectronic applications and photoactivated materials. Chromium(III) complexes can be developed to show sharp luminescent bands as a result of relaxation from the spin-forbidden doublet excited states, namely 2E/2T1, with lifetimes into the microsecond range. In addition, the high natural abundance of chromium in comparison with precious metals such as FTIR(III), Re(I) and Ru(II) makes it a desirable alternative element for the development of luminescent complexes. This thesis describes three series of Cr(III) complexes which are differentiated by the class of ligand utilised, namely Schiff-bases, polypyridyls and bis-pyridyl isoindolines (BPI). The polypyridyl and BPI series of complexes exhibited emission from doublet excited states. Through correlation of the geometry of the complexes and their emission maxima it was found that BPI ligands provide a more covalent character to the Cr-N bonds leading to emission maxima shifted further into the NIR-II region (> 900 nm, microsecond range lifetimes). This was further supported by EPR measurements at various MW frequencies where complexes which exhibited a significant increase of the covalency of the Cr-N bond (BPI series) led to lower D-values (~0.1 cm-1 ) compared to those of the polypyridyl series which possess D-values of ~0.4 cm-1 . Having calculated the nephelauxetic effect parameter for the BPI series (0.7-0.75) and compared it with previously reported parameter for [Cr(phen)3] 3+ (0.85), it was evident that the BPI series presented an increased covalent character of the Cr-N bond introduced via the isoindoline moiety. This led to a conclusion that the decrease in the nephelauxetic effect parameter evidenced a reduced inter-electronic repulsion responsible for an impressive red-shift of the emission maxima and lower D-values.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Funders:	EPSRC
Date of First Compliant Deposit:	31 October 2023
Last Modified:	01 Nov 2023 12:39
URI:	https://orca.cardiff.ac.uk/id/eprint/163597

Actions (repository staff only)

Edit Item