1 Supplementary Information A covalently linked dimer of silver nanocluster: [Ag 25 (DMBT) 18 ] - Mohammad Bodiuzzaman a , Abhijit Nag a , Raghu Narayanan Pradeep a , Ankush Chakraborty b , Ranjit Bag b , Ganesan Paramasivam a , Ganapati Natarajan a Govindasamy Sekar b , Sundargopal Ghosh b and Thalappil Pradeep* a a Department of Chemistry, DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Indian Institute of Technology Madras, Chennai 600036, India b Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India *Email: pradeep@iitm.ac.in Table of contents: Name Description Page no. 2 Experimental section 2-6 Table S1 The aspicule ligand locants and atom numbers 7 Table S2 The total energies of the isomers 7 Figure S1 Characterization of the [Ru(bpy) 2 bpy(CH 2 SH) 2 ] 2+ complex 8 Figure S2 Characterization of the [Ag 25 (DMBT) 18 ] - cluster 9 Figure S3 Optical absorption spectra of Ag 25 (DMBT) 18 after addition of 1,4 dithiol and biphenyl-4,4-dithiol 10 Figure S4 Comparison of IR spectroscopy of the dimer and linker 11 Figure S5 ESI MS and UV-vis of [Ru(bpy) 2 bpy(CH 2 SH) 2 ] added [Au 25 (BT) 18 ] 12 Figure S6 Powder X-ray diffraction of Ag 25 monomer and Ag 25 dimer 13 Electronic Supplementary Material (ESI) for ChemComm. This journal is © The Royal Society of Chemistry 2019