Photophysical Enhancement of Triplet Emitters by Coordination‐Driven Self‐Assembly

Abstract

The quantum yields of organic fluorophores used as donors in coordination-driven self-assembly often suffer from the heavy atom effect of nearby metal sites. Here, the role of intersystem crossing from a deactivating process to one that delivers emissive triplet states was reversed. A phosphorescent trans bis-N-heterocyclic carbene platinum(II) compound, Pt(dhim) (C≡C-4-py) (D1; dhim=1,3-dihexyl-2-H-imidazol-2-ylidene), was used along with other linear donors 4,4'-bipyridine (D2) and 1,4-bis(4-pyridyl ethynyl)benzene (D3) in self-assembly reactions with Pt(dtbpy)X acceptors (dtbpy=4,4'-di-tert-butyl-2,2'-bipyridine) to afford three metallacycles. Photophysical investigations revealed that, although the building blocks used to construct M1 have relatively low quantum yields (Φ=1.2 and <1 % for D1 and 2, respectively), the metallacycle has a quantum yield of 14 %. This increase reflects a change in radiative rate constant from 3.6×10 s for D1 to 2.1×10 s for M1.

Heterometallic Ru–Pt metallacycle for two-photon photodynamic therapy

“…This result is in good agreement with the direct method. The Φ Δ of 1 is considerably higher than many organic and organometallic compounds including [Ru(bpy) 3 ] 2+ (14,15,27), presumably due to the enhanced intersystem crossing process by introduction of Pt (21,22). The molecular ability to initiate the PDT process following two-photon excitation is often evaluated using a merit parameter σ 2 × Φ Δ (29).…”

“…First, Pt(II) may endow the ensemble with favorable photophysical properties for biomedical applications, such as red-shifted emission and enhanced TPA activities compared with analogous small molecules (19,20). Second, as a heavy atom, the Pt would also promote intersystem crossing, which results in more efficient ROS generation (21,22). Third, the rigid, planar macrocyclic structure of 1 may…”

Multicomponent Porphyrin‐Based Tetragonal Prismatic Metallacages and their Photophysical Properties

“…The Φ Δ values of metallacages 4 a , 4 b and 4 c were calculated to be 0.73, 0.62 and 0.73 in DMSO, respectively. The Φ Δ values of metallacages 4 a and 4 c are even higher than that of TPP because the Pt(II) would promote intersystem crossing, benefiting better 1 O 2 generation efficiency for metallacages. Considering the potential anticancer activity of Pt(PEt 3 ) 2 (OTf) 2 , these metallacages could be potentially used as cancer theranostic agents including bio‐imaging, chemotherapy and photodynamic therapy.…”

Crystal structure of bis(acetonitrile-κN)(4,4′-di-tert-butyl-2,2′-bipyridine-κ2 N,N′)platinum(II) bis(tetrafluoridoborate) packing as head-to-head dimers

“…The title compound is soluble in a diverse range of solvents and possesses exchangeable acetonitrile ligands for facile incorporation of novel ligands to develop new and diverse behaviors of platinum(II) complexes. The solubility and apt geometry of the (dbbpy)platinum(II) complex make it a desirable building block for coordination-driven self-assembly of homo-metallic (Zhang, et al, 2017) and hetero-metallic (Bera et al, 2001) supramolecular complexes. This platinum(II) diimine can also be combined with dithiolene ligands to study methylation kinetics (Stace, et al, 2016), generate charge-transfer materials (Smucker, et al, 2003), or make model complexes for examining photophysical properties (Lazarides, et al, 2011;Yang et al, 2014).…”