Elucidating non-radiative decay in near-infrared lumiphores: Leveraging new design principles to develop a telecom band organic dye laser

Variable Peripheral Ligand Donation Tunes Electronic Structure and NIR II Emission in Tetrathiafulvalene Tetrathiolate Diradicaloids

“…We synthesized the Pt phosphine dichloride precursors based on modified literature procedures (see the Supporting Information (SI)), using commercially available, p -substituted triarylphosphines. − The Pt precursors were then reacted with (SnBu 2 ) 2 TTFtt and subsequently oxidized with two equivalents of [Fc BzO ][BAr 4 F ], according to previously established procedures, to give the dicationic complexes 1 – 4 (see Figure ). These complexes, along with previously reported analogues 5 and 6 , form a series of p -substituted triphenylphosphine-capped dications. , These complexes were characterized by a suite of techniques, including multinuclear NMR spectroscopy and single-crystal X-ray diffraction (SXRD). SXRD-quality crystals were grown by layering hexanes or petroleum ether over the desired complex dissolved in dichloromethane (DCM), forming a slow diffusion gradient.…”

“…We designed our study based off current commercially available triarylphosphines with variable substituents in the para position. We already had used two such analogues to synthesize new TTFtt complexes for previous studies (CF 3 and H with Hammett parameters, σ p , 0.54 and 0, respectively). ,, We expanded the series with the addition of four new analogues for a total range of Hammett parameters from −0.27 to 0.54 …”

“…This NIR II emission is realized on such a small core due to heavy heteroatom substitution, which compresses the π system and bathochromically shifts emission . Furthermore, the compact scaffold size minimizes deleterious vibrational modes that are believed to enhance nonradiative decay in this region . Ultimately, the capping of this small scaffold with Pt centers maintains this bright, organic-based NIR II emission, while allowing for tunability on the open capping ligand sites.…”

“…Our lab has recently reported a compact, modular scaffold that emits deep into the NIR II, while maintaining high photoluminescence quantum yields (PLQYs) for the region . While our previously reported analogues displayed some modularity in electronic structure and photophysical properties, we wanted to test whether systematic perturbations would enable rational tuning of these properties over a wider range and thus allow for more targeted applications. , Using triarylphosphines as a set of tunable capping ligands, we introduced various electron-donating and -withdrawing groups to the para position of the aryl rings. This approach enabled the synthesis of four new Pt-capped tetrathiafulvalene tetrathiolate (TTFtt) dicationic complexes.…”

“…This approach enabled the synthesis of four new Pt-capped tetrathiafulvalene tetrathiolate (TTFtt) dicationic complexes. We then compared the electronic structures and photophysical properties of these complexes with two previously reported examples for a total comparison across six analogues. , …”