Electronic and steric effects of Platinum(II) di-yne and poly-yne substituents on the photo-switching behaviour of stilbene: Experimental and theoretical insights

A series of mono-, di-, and poly(platina-ynes) incorporating stilbene spacer units with the formulae trans-[R–CC–Pt(PBu3)2-CC–R] (R = (E)-1,2-diphenylethene), trans-[(Ph)-(Et3P)2PtCC–R–CCPt(PEt3)2(Ph)] (R = (E)-1,2-diphenylethene), and trans-[–(PnBu3)2PtCC–R–CC–]n (R = (E)-1,2-diphenylethene), respectively, have been synthesized and characterized to explore the effects of ligand topology on the photoisomerization and photophysical properties of these materials. The structural and photophysical properties of the complexes have been investigated and compared with those of the previously reported mono-, di- and poly(platina-ynes) incorporating azobenzene spacers. We found that the organometallic species 1M, 2M and 1P undergo topology-dependent reversible trans-to-cis photoisomerization in CH2Cl2 solution. Computational modelling supported the experimental findings.