Influence of O−H⋅⋅⋅Pt interactions on photoluminescent response in the (Et₄N)₂{[Pt(bph)(CN)₂][phenylene-1,4-diresorcinol]} framework

Graphical Abstract

Photoluminescence (PL) of the [Pt^II(C C)(CN)₂]^2– complexes are tunable via the modification of ligands, intermolecular interactions and type of molecular aggregation. SC XRD, PL, and DFT unite to discriminate the rare _RO−H⋅⋅⋅Pt synthons to be responsible for the emission redshift, the _RO−H⋅⋅⋅N_complex synthons being less critical. The plausible continuum of _RO−H⋅⋅⋅Pt contacts is indicated as the broad space for the PL continuous tuning.

Abstract

Tunable photoluminescence (PL) is one of the hot topics in current materials science, and research performed on the molecular phases is at the forefront of this field. We present the new (Et₄N)₂[Pt^II(bph)(CN)₂]⋅rez3⋅¹/₃H₂O (Pt2rez3) (bph=biphenyl-2,2’-diyl; rez3=3,3”,5,5”-tetrahydroxy-1,1’:4’,1”-terphenyl, phenylene-1,4-diresorcinol coformer, a linear quaternary hydrogen bond donor) co-crystal salt based on the recently appointed promising [Pt^II(bph)(CN)₂]^2– luminophore. Within the extended hydrogen-bonded subnetwork [Pt^II(bph)(CN)₂]^2– complexes and rez3 coformer molecules form two types of contacts: the _rez3O−H⋅⋅⋅N_complex ones in the equatorial plane of the complex and non-typical _rez3O−H⋅⋅⋅Pt ones along its axial direction. The combined structural, PL, and DFT approach identified the _rez3O−H⋅⋅⋅Pt synthons to be crucial in promoting the noticeable uniform redshift of bph ligand centered (LC) emission compared to the LC emission of the (Et₄N)₂[Pt^II(bph)(CN)₂]⋅H₂O (Pt2) precursor, owing to the direct interference of the phenol group with the Pt^II-bph orbital system via altering the CT processes within. The high-resolution emission spectra for Pt2 and Pt2rez3 were successfully reproduced at 77 K by using the Franck-Cordon expressions. The possibility to tune PL properties along the plausible continuum of _rez3O−H⋅⋅⋅Pt synthons is indicated, considering various scenarios of molecular occupation of the space above and below the complex plane.