HOMO inversion as a strategy for improving the light-absorption properties of Fe(ii) chromophores

Abstract

Substitution of π-conjugated donor groups onto the polypyridine ligands in Fe(ii) complexes inverts the HOMO character and improves the light-absorption.

Retracted Article: Facile preparation of bithiazole-based material for inkjet printed light-emitting electrochemical cell

“…48 It may indicate that enlarging the conjugation length and electron density with these donor groups plays an important role in increasing the f PL . 49 Moreover, those with high f PL may be suitable for application as efficient light-emitting material in LECs. 50 In addition, time-resolved measurements of the donor lifetime (s) in 1a-1c were carried out, and their corresponding values are given in Table S1.…”

Is Iron the New Ruthenium?

“…[37] Recently,J akubikova and co-workersr eported on ac omputationals tudy focused on improving the optical absorption properties of Fe II polypyridines;t his work provided particularly interesting insights regarding the importance of the p-donation properties of the ligands. [35] The tpy ligandss ubstituted with furan, thiophene, and selenophenes (Figure 7b)w ere found to have occupied p orbitals that were energetically better alignedw ith the t 2g orbitals on Fe II ;t hus leadingt o stronger metal-ligand p interactions andaconsequent increase of the HOMO energy (Figure 3d). This results in multiple mixed MLCT/ILCT( ILCT = intraligand charge transfer) transitions in the calculated absorption spectrum.…”

“…Examples of candidatec omplexes predicted to be interesting by calculations:a)[Fe(N^C^N)(N^N^C)]; [17a, b] b) complexeswith p-donating ligands,some of them leadingt o" HOMO inversion". [35] NHCs. [39] The uncommon {Fe(bpy)Cl 2 }i ntermediate gave access to the heteroleptic [Fe(btz) 2 (bpy)] 2 + complex (Figure 8a)w ith a 3 MLCT lifetime of 13 ps,w hichw as 100 times longert han that in [Fe(bpy) 3 ] 2 + .T he new complex is photochemically robust, even during overnight laser experiments.…”

Excited‐State Kinetics of an Air‐Stable Cyclometalated Iron(II) Complex

“…From an application point of view,b is(tridentate) ligand-iron(II) combinations are superior to tris(bidentate) iron(II) complexes,a st he formero nes are typically more inert toward substitution. [3] Since recorded 3 MLCT lifetimes are so far reported for bidentate complexes, [4] further lifetime engineeringin tridentate-coordinated Fe II complexes [5,6] and derivatives thereofa re thus highlyi mportant.…”

“…For a 5 MC state typicallyananosecondl ifetimei se xpected due to the double spin state change required in the relaxation. Thus, the very short lifetimeo f1 2psf or 2 makes ac ontribution of aq uintet 5 MC state unlikely [8,9] as it would additionally requirea ne longation of all iron-ligand bonds,w hich is unlikely due to the presenceo ft he FeÀC cm bond.…”