T ½ Tuning in a Synergistic BODIPY‐Tetrazole Fe(II) Spin‐Crossover‐Photoluminescence System via Co‐Ligand Variation
Year: 2025
Type: article
Abstract: Bifunctional materials combining spin crossover (SCO) and photoluminescence (PL), offering noncontact and highly sensitive spin‐state detection, are promising candidates for application in photonic devices. However, independently tuning the SCO and PL properties to achieve synergistic SCO‐PL behavior remains challenging. Herein, we present a series of heteroleptic Fe(II) coordination compounds with the general formula [Fe( L ) 4 ( R CN) 2 ](ClO 4 ) 2 •n R CN, bearing four BODIPY‐derived fluorophores L ( L = 4,4‐difluoro‐1,3,5,7‐tetramethyl‐8‐[(1 H ‐tetrazol‐1‐yl)methyl]‐4‐bora‐3a,4a‐diaza‐ s ‐indacene) in the equatorial positions and variable R CN co‐ligands (CH 3 CH 2 CN, CH 2 CHCN, CH 3 (CH 2 ) 2 CN, PhCN) in the apical positions. The systematic variation of the co‐ligand modulates steric and/or electronic effects, thereby influencing the SCO behavior without perturbing the PL characteristics. Magnetic susceptibility measurements revealed T 1/2 = 220 K and 270 K for R = CH 3 CH 2 and R = CH 2 CH, respectively, indicating that electronic effects modulate T 1/2 . Conversely, for R = Ph and R = CH 3 (CH 2 ) 2 the SCO capability is progressively lost, with the latter showing no spin‐switching at all. Temperature‐dependent PL studies display an increase in emission upon the SCO, most pronounced for [Fe( L ) 4 (CH 3 CH 2 CN) 2 ](ClO 4 ) 2 •2CH 3 CH 2 CN, which can be attributed to electronic coupling between the SCO center and the fluorophore. This work establishes a single‐molecule SCO‐PL platform, in which the SCO behavior can be tuned independently from the PL response, paving the way for tailored molecular sensors and optical switches.
Source: Chemistry - A European Journal
Authors: Martin Huber, Matthias Schöbinger, Berthold Stöger, Michael Reissner, Peter Weinberger
Institution: TU Wien
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,640
OpenAlex ID: W4415063246