Article pubs.acs.org/Organometallics
Linear Bimetallic Alkynylplatinum(II) Terpyridyl Complexes Bearing p‑Phenylene Ethynylene Oligomers: Synthesis, Characterization, Aggregation, and Photophysical Properties Peng Xu, Haotian Wu, Hongxing Jia, Shifan Ye, and Pingwu Du* Department of Materials Science and Engineering, Department of Chemistry, CAS Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei, People’s Republic of China 230026 S Supporting Information *
ABSTRACT: The series of luminescent bimetallic alkynylplatinum(II) terpyridyl complexes [(tBu3-tpy)PtCC(ArCC)nPt(tBu3-tpy)](PF6)2 (I−IV; tBu3-tpy = 4,4′,4″-tritertbutyl2,2′: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 steadystate spectroscopy and transient spectroscopy. Concentrationdependent 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.
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light-emitting diodes,15 and self-assembling soft matters.16 All of these applications are considered to be closely related to long-lived excited states or d8−d8 metal−metal interactions and/or π−π stacking.17 Aside from the considerable work carried out on the development of simple monometallic alkynylplatinum(II) complexes, multinuclear alkynylplatinum(II) complexes in which transition-metal centers are connected by a rigid or flexible backbone have been found to show very interesting properties.15a,18 The Yam group19 and the Yang group20 reported a series of multinuclear alkynylplatinum(II) complexes bearing a rigid branched backbone, which showed enhanced gelation, two-photon absorption, or two-photoninduced luminescence properties compared with mononuclear metal complexes. The Gladysz group21 reported a series of trans,trans-(C6F5)(R3P)2Pt(CC)nPt(PR3)2(p-tol) (R = p-tol) complexes, which exhibited phosphorescence from triplet states concentrated on the C4 segments. Studies on binuclear alkynylplatinum(II) terpyridyl complexes with double metal centers which are bridged by long linear conjugated oligomerd are relatively rare.18a,22 Herein, we report the synthesis, characterization, aggregation, and photophysical properties of linear binuclear alkynylplatinum(II) complexes bearing p-phenylene ethynylene oligomers, in which a terpyridyl group is used as the second ligand.
INTRODUCTION Research on photofunctional transition-metal complexes has been an active field in the past few decades.1 Among them, platinum(II) complexes coordinated to nitrogen or phosphorus donor atoms have been widely studied because square-planar platinum(II) complexes exhibit rich photophysical and photochemical properties.2 One early example is the binuclear derivative [Pt2(μ-P2O5H2)4]4− (often called “platinum pop”), showing long-lived excited states in solution, which has been studied for various photoinduced chemical reactions such as C−H bond cleavage of isopropyl alcohol and halogen atom abstraction.2b Luminescent excited states were later found in platinum(II) diimine and terpyridyl complexes, but their lifetimes are usually short (
