Abstract: Synthesis and reactivity study of multi-3D-cavity coordination cages is an area of current interest.1,2 A few double, triple and quadruple cavity cages of PdnLm variety are prepared from Pd(II) and a symmetrical or unsymmetrical ligand. Mixed ligated double and triple cavity cages of Pdn(La)x(Lb)y variety prepared by integrative self-sorting are also known but only limited in number in view of the challenge involved in their design.1 We visualize these multi cavity cages as conjoining of two or more single cavity cages. Conjoining of one binuclear Pd2L4 unit with one or two Pd2L4 unit(s) of same/different sizes is known;1 similarly, conjoining of a Pd3L6 unit with one, two or three Pd2L4 unit(s) is also known.2 In the present work our target was to prepare new multicavity cages of known and unreported designs. One among the new designs prepared in this work is conjoining of two Pd3L6 units with each other. To achieve our objectives, a set of reported3 single cavity Pd2L4, Pd3L6, Pd4L8 and Pd6L12 type cages prepared from simple bidentate ligands were chosen. The bidentate ligands were further derivatized to make tridentate and tetradentate ligand systems. Complexation of Pd(II) with one type as well as mixed types of ligand(s) were undertaken by keeping logical design principles in mind. In the course of the work, we prepared double cavity Pd3L4, Pd4(La)2(Lb)4, Pd5(La)4(Lb)4. A few other Pdn(La)x(Lb)y designs were attempted for which we propose structural formula but there is a lack of proper evidence. Among the designs, the most notable one is Pd5(La)4(Lb)4 type double cavity cage. This pentanuclear cage could be prepared without any external guest for certain ligand systems, whereas for another set of ligands an externally added anionic guests was required.
References:
1. Sharma, S.; Sarkar, M; Chand, D. K. Chem. Commun. 2023, 59, 535-554.
2. Samantray, S.; Krishnaswamy, S.; Chand, D. K. Nat. Commun. 2020, 11, Article 880.
3. Prusty, S. K. PhD Thesis, New Rummy Game, 2017.