title: Unusual reactivity of dithiol protected clusters in comparison to monothiol protected clusters: studies using Ag51(BDT)19(TPP)3and Ag29(BDT)12(TPP)4.
abstract: We report the synthesis and unique reactivity of a new green dithiol protected cluster (DTPC), Ag51(BDT)19(TPP)3(BDT and TPP are 1,3-benzenedithiol and triphenylphosphine, respectively). The cluster composition was confirmed by electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometric studies as well as by other supporting data. Surprisingly, the chemical reactivity between this DTPC and Au25(SR)18involves only metal ion exchange in Au25(SR)18without any ligand exchange, while reactions between monothiol protected clusters (MTPCs) show both metal and ligand exchange, an example being the reaction between Ag25DMBT18and Au25PET18(where DMBT and PET are 2,4-dimethylbenzenethiol and phenylethanethiol, respectively). The conclusions have been confirmed by the reaction of another DTPC, Ag29(BDT)12(TPP)4with Au25BT18(where BT corresponds to butanethiol) in which only metal exchange happens in Au25BT18. We also show the conversion of Ag51(BDT)19(TPP)3to Ag29(BDT)12(TPP)4in the presence of a second monothiol, DMBT which does not get integrated into the product cluster. This is completely different from the previous understanding wherein the reaction between MTPCs and a second thiol leads to either mixed thiol protected clusters with the same core composition or a completely new cluster core protected with the second thiol. The present study exposes a new avenue of research for monolayer protected clusters, which in turn will give additional impetus to explore the chemistry of DTPCs.
authors.affiliation: DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.
authors.forename: Atanu
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.
authors.forename: Debasmita
authors.initials: D
authors.lastname: Ghosh
authors.affiliation: DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.
authors.forename: Esma
authors.initials: E
authors.lastname: Khatun
authors.affiliation: DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.
authors.forename: Papri
authors.initials: P
authors.lastname: Chakraborty
authors.affiliation: DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.
authors.forename: Thalappil
authors.initials: T
authors.lastname: Pradeep