Structure-Properties Correlation in Metal-Organic Frameworks and Atom-Precise Metal Nanoclusters

We have successfully done the complete transmetallation at the node of an alkaline earth metal based MOF with Tb3+ ions for the first time without changing the parent framework structure. The whole exchange process was followed through optical microscope and through single crystal manner.1 The parent compound has significant local ferroelectric and piezoelectric properties. The new Tb exchanged MOF after metal metathesis possess multi-functional features including enhanced photoluminescence, strong magnetic frustration and switchable ferroelectric properties and it acts as a selective sensor for phosphate anion. The ferroelectric turn off phenomenon after metal exchange could be due to the absence of organic cation in the pore of the framework, whose motion was responsible for the ferroelctricity. Thus this work not only provides a tool to functionalize a MOF which can have potential applications in high speed magneto-optic devices but also elucidates the formation mechanism of resulting MOF and it’s chemical properties. Finally I shall discuss ne example of new magneto-electronics MOF based material.

Ligand stabilized water soluble Pt nanoclusters were synthesized and characterized through electrospray ionization mass spectrometry.2 Glutathione was used as the ligand, and Pt5(SG)10, and Pt6(SG)12 clusters were synthesized. Theoretical investigations found that these clusters do not possess a metal core, but rather are most stable in a ring structure. The clusters are stabilized through the –SH group and forming square planar structure around each Pt atom to form a ring. We found interesting strong luminescence from this cluster by the mechanism of aggregation-induced emission. The optical properties of these nanoclusters can be employed for several applications such as humidity sensor, biological sensing, fabrication of LEDs, etc.

A new tert-butylbenzene thiol (TBBT) protected gold nanocluster was synthesized from Au25(PET)18 (PET = 2-phenylethane thiol) cluster by ligand exchange methodology. The formation of the new cluster was confirmed by the emergence of new optical behaviour. This ligand exchange can greatly influence the properties of the nanocluster thereby increasing their efficiency in catalytic applications. Therefore the mechanistic pathway for these kind of transformations are very important and will be discussed in details in the presentation.

[1] (a) K. S. Asha, R. Bhattacharjee, S. Mandal, Angew Chem. Int. Ed. 2016, 55, 11528; (b) Asha K.S., Niyaz Ahmed, Ramesh Nath, D. Kuznetsov, S. Mandal, Inorg. Chem. 2017, 56, 7316.

[2] A. George, K. S. Asha, A. C. Reber, S. R. Biltek, A. F. Pedicini, A. Sen, S. N. Khanna, S. Mandal Nanoscale, 2015, 7, 19448-19452.

20180509_특별세미나_Sukhendu Mandal.pdf