Linear Bimetallic Alkynylplatinum(II) Terpyridyl Complexes Bearing p‑Phenylene Ethynylene Oligomers: Synthesis, Characterization, Aggregation, and Photophysical Properties

The series of luminescent bimetallic alkynylplatinum­(II) terpyridyl complexes [(tBu3-tpy)­PtCC­(ArCC)nPt­(tBu3-tpy)]­(PF6)2 (I–IV; tBu3-tpy = 4,4′,4″-tritertbutyl-2,2′:6′,2″-terpyridine, Ar = C6H2(n-hexyloxy)2-2,5), in which two platinum­(II) centers are linked by p-phenylene ethynylene oligomers, were synthesized and characterized. Their electronic absorption and luminescent behaviors were studied by steady-state spectroscopy and transient spectroscopy. Concentration-dependent emission data show that all of the complexes form self-assembled aggregates in certain concentration ranges. Complex IV, bearing a longer p-phenylene ethynylene oligomer, exhibits higher propensity in comparison to I–III to form aggregates at a concentration of >1 × 10–5 M, probably resulting from stronger metal–metal interactions and π–π stacking. All four of the complexes displayed biexponential decays with lifetimes in the range of nanoseconds in dilute solutions.