Photophysical Properties of Self-Assembled Multinuclear Platinum Metallacycles with Different Conformational Geometries

Abstract

In this work, spectroscopic techniques and quantum chemistry calculations were used to investigate the photophysical properties of various multinuclear platinum complexes with different conformational geometries. This suite of complexes includes a Pt−pyridyl square, a Pt−carboxylate triangle, and a mixed Pt−pyridyl−carboxylate rectangle, as well as two mononuclear Pt model complexes. Studying the individual molecular precursors in the context of larger assemblies is important to provide a complete understanding of the factors governing the observed photophysical properties of a given system. The absorption and emission bands of the parent linear dipyridyl donor (ligand 1) are largely preserved in the [4 + 4] square and the multicomponent [4 + 2 + 2] rectangle (3 and 4, respectively), with significant red shifts. The [3 + 3] Pt− carboxylate triangle containing p-phthalic acid is nonemissive. Phosphorescence and nanosecond transient spectroscopy on 3 and 4 reveal that the introduction of platinum atoms enhances spin−orbital coupling, thereby increasing the rate of intersystem crossing. This phenomenon is consistent with the low fluorescence quantum yields and short fluorescence lifetimes of 3 and 4. Moreover, the electronic structures for the ground state and low-lying excited states of these compounds were studied using quantum chemistry calculations. The fluorescent states of the platinum complexes are local excited states of ligand-centered π−π* transition features, whereas the nonfluorescent states are intramolecular charge-transfer states. These low-lying intramolecular charge-transfer states are responsible for the nonemissive nature of small molecules 1 and 2 and triangle 5. As the interactions between these components determine the properties of their corresponding assemblies, we establish novel excitedstate decay mechanisms which dictate the observed spectra.

2D l‐Di‐toluoyl‐tartaric acid Lanthanide Coordination Polymers: Toward Single‐component White‐Light and NIR Luminescent Materials

“…[25,26] Herein,t he singlet ( 1 pp*) energy level of H 2 L (270 nm, 1 pp* = 37 040 cm À1 )i se stimated by referring to its wavelength of absorbance edge in the UV spectrum (Figure S2). The triplet ( 3 pp*) energy level of H 2 L( 438 nm: 3 pp* = 22 830 cm À1 )i sd etermined by the low-wavelength emission peak of the phosphorescence of the Gd analog at 77 K ( Figure S8) process is effective in this ligand (Scheme 1).…”

In vivo anticancer activity of rhomboidal Pt(II) metallacycles

“…Moreover, recent reports have demonstrated that platinum-based SCCs can act as effective hosts for guests and have interesting photophysical properties (37)(38)(39)(40)(41)(42). In particular, highly emissive rhomboids based on aniline-containing donors and Pt-based metal acceptors have…”

Insight into the excited-state intramolecular double-proton transfer of the 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol: one-step or stepwise mechanism?

“…The excitedstate intramolecular proton transfer (ESIPT) attracts much attention particularly due to its dual emission with large Stokes' shift, which leads to its significant applications in molecular probes [5,[13][14][15][16], laser dyes [17][18][19], luminescent materials [20][21][22], chemosensors [23][24][25][26][27][28][29][30][31] and molecular logic gates [32], etc. Hence, the mechanism investigation of ESIPT is of vital importance to design, synthesize and regulate desired luminescent molecules [33][34][35][36][37].…”