%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 %0 Journal Article %J ACS Nano %D 2021 %T Light-Activated Intercluster Conversion of an Atomically Precise Silver Nanocluster %A Arijit Jana %A Madhuri Jash %A Ajay Kumar Poonia %A Ganesan Paramasivam %A Md Rabiul Islam %A Papri Chakraborty %A Sudhadevi Antharjanam %A Jan Machacek %A Sundargopal Ghosh %A Kumaran Nair Valsala Devi Adarsh %A Tomas Base %A Thalappil Pradeep %K carboranes silver nanoclusters intercluster conversion near-infrared emission luminescence ultrafast electron dynamics %X

Noble metal nanoclusters protected with carboranes, a 12-vertex, nearly icosahedral boron–carbon framework system, have received immense attention due to their different physicochemical properties. We have synthesized ortho-carborane-1,2-dithiol (CBDT) and triphenylphosphine (TPP) coprotected [Ag42(CBDT)15(TPP)4]2– (shortly Ag42) using a ligand-exchange induced structural transformation reaction starting from [Ag18H16(TPP)10]2+ (shortly Ag18). The formation of Ag42 was confirmed using UV–vis absorption spectroscopy, mass spectrometry, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, and multinuclear magnetic resonance spectroscopy. Multiple UV–vis optical absorption features, which exhibit characteristic patterns, confirmed its molecular nature. Ag42 is the highest nuclearity silver nanocluster protected with carboranes reported so far. Although these clusters are thermally stable up to 200 °C in their solid state, light-irradiation of its solutions in dichloromethane results in its structural conversion to [Ag14(CBDT)6(TPP)6] (shortly Ag14). Single crystal X-ray diffraction of Ag14 exhibits Ag8–Ag6 core–shell structure of this nanocluster. Other spectroscopic and microscopic studies also confirm the formation of Ag14. Time-dependent mass spectrometry revealed that this light-activated intercluster conversion went through two sets of intermediate clusters. The first set of intermediates, [Ag37(CBDT)12(TPP)4]3– and [Ag35(CBDT)8(TPP)4]2– were formed after 8 h of light irradiation, and the second set comprised of [Ag30(CBDT)8(TPP)4]2–, [Ag26(CBDT)11(TPP)4]2–, and [Ag26(CBDT)7(TPP)7]2– were formed after 16 h of irradiation. After 24 h, the conversion to Ag14 was complete. Density functional theory calculations reveal that the kernel-centered excited state molecular orbitals of Ag42 are responsible for light-activated transformation. Interestingly, Ag42 showed near-infrared emission at 980 nm (1.26 eV) with a lifetime of >1.5 μs, indicating phosphorescence, while Ag14 shows red luminescence at 626 nm (1.98 eV) with a lifetime of 550 ps, indicating fluorescence. Femtosecond and nanosecond transient absorption showed the transitions between their electronic energy levels and associated carrier dynamics. Formation of the stable excited states of Ag42 is shown to be responsible for the core transformation.

%B ACS Nano %V 15 %P 15781-15793 %G eng %U https://pubs.acs.org/doi/abs/10.1021/acsnano.1c02602 %N 10 %9 Full Article %R https://doi.org/10.1021/acsnano.1c02602 %0 Journal Article %J Chemical Science %D 0 %T Carborane-thiol protected copper nanoclusters: Stimuli-responsive materials with tunable phosphorescence %A Arijit Jana %A Madhuri Jash %A Wakeel A 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 carborane %K Cluster %K Copper %K Phosphorescence %K Responsive %K thiol %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 %G eng %U https://pubs.rsc.org/en/content/articlelanding/2023/sc/d2sc06578a %R https://doi.org/10.1039/D2SC06578A