%0 Journal Article %J Chemical Science %D 2023 %T Carborane-thiol protected copper nanoclusters: Stimuli-responsive materials with tunable phosphorescence %A Arijit Jana %A Madhuri Jash %A Wakeel Ahmed Dar %A Jayoti Roy %A Papri Chakraborty %A Paramasivam Ganesan %A Sergei Lebedkin %A Kaplan Kirakci %A Sujan Manna %A P. K. Sudhadevi Antharjanam %A Jan Machacek %A Monika Kucerakova %A Sundargopal Ghosh %A Kamil Lang %A Manfred Kappes %A Tomas Base %A T. Pradeep %K boron %K Cluster %K Copper %K Cu4L4 %K Phosphorescence %K Responsive %X

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu4@oCBT, Cu4@mCBT and Cu4@ICBT, protected by nearly isomeric carborane thiols: ortho-carborane-9-thiol, meta-carborane-9-thiol and ortho-carborane 12-iodo 9-thiol, respectively. They have a square planar Cu4 core and a butterfly-shaped Cu4S4 staple, which is appended with four respective carboranes. For Cu4@ICBT, strain generated by the bulky iodine substituents on the carboranes makes the Cu4S4 staple flatter in comparison to other clusters. High-resolution electrospray ionization mass spectrometry (HR ESI-MS) and collision energy-dependent fragmentation, along with other spectroscopic and microscopic studies confirm their molecular structure. Although none of these clusters show any visible luminescence in solution, bright μs-long phosphorescence is observed in their crystalline forms. The Cu4@oCBT and Cu4@mCBT NCs are green emitting with quantum yields (Ф) of 81 and 59 %, respectively, whereas Cu4@ICBT is orange emitting with a Φ of 18 %. Density functional theory (DFT) calculations reveal the nature of their respective electronic transitions. The green luminescence of Cu4@oCBT and Cu4@mCBT clusters get shifted to yellow after mechanical grinding, but it is regenerated after exposure to solvent vapour, whereas the orange emission of Cu4@ICBT is not affected by mechanical grinding. Structurally flatten Cu4@ICBT didn’t show mechonoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 °C. The Cu4@oCBT retained green emission even upon heating to 200 °C under ambient conditions, while Cu4@mCBT changed from green to yellow in the same window. This is the first report on structurally flexible carborane thiol appended Cu4 NCs having stimuli-responsive tunable solid-state phosphorescence.

%B Chemical Science %V 14 %P 1613-1626 %8 12/2023 %G eng %U https://pubs.rsc.org/en/content/articlelanding/2023/sc/d2sc06578a %9 Article %& 1613 %R https://doi.org/10.1039/D2SC06578A