Abstract
Structurally divergent molecules containing bulky substituents tend to produce porous materials via frustrated packing. Two rigid tetrahedral cores, tetraphenylmethane and 1,3,5,7-tetraphenyladamantane, grafted peripherally with four (trimethylsilyl)ethynyl moieties, were found to have only isolated voids in their crystal structures. Hence, they were modified into tecton-like entities, tetrakis(4-(iodoethynyl)phenyl)methane [I4TEPM] and 1,3,5,7-tetrakis(4-(iodoethynyl)phenyl)adamantane [I4TEPA], in order to deliberately use the motif-forming characteristics of iodoethynyl units to enhance crystal porosity. I4TEPM not only holds increased free volume compared to its precursor, but also forms one-dimensional channels. Furthermore, it readily co-crystallizes with Lewis basic solvents to afford two-component porous crystals.
Highlights
According to Kitaigorodskii’s principle of close packing [1,2,3,4,5], molecules in crystals tend to dovetail and pack as efficiently as possible in order to maximize attractive dispersion forces and to minimize free energy
The solid-state packing behavior of tetrakis(4-((trimethylsilyl)ethynyl)phenyl)methane [TMS4TEPM] and 1,3,5,7-tetrakis(4-((trimethylsilyl)ethynyl)phenyl)adamantane [TMS4TEPA] showed some degree of extrinsic porosity. These two molecules were converted into tecton-like derivatives with XB capability, I4TEPM and I4TEPA, in order to investigate the power of iodoethynyl recognition sites in the context of solid-state packing and extrinsic porosity
Even though I4TEPA tends not to form crystalline unary or binary solids, I4TEPM crystallizes into porous solids in its neat form as well as with suitable co-formers
Summary
According to Kitaigorodskii’s principle of close packing [1,2,3,4,5], molecules in crystals tend to dovetail and pack as efficiently as possible in order to maximize attractive dispersion forces and to minimize free energy. The packing of molecules designed to bear sufficiently large and dimensionally fixed inner cavities or clefts (e.g., molecular cages and bowl-shaped compounds) can lead to porous structures [12,13,14]. Another viable synthetic strategy towards MPMs is to employ molecules with bulky, divergent and/or awkward shapes so that they no longer have the ability to pack tightly. Molecules such as 4-p-Hydroxyphenyl-2,2,4-trimethylchroman (Dianin’s compound) [15,16], tris(o-phenylenedioxy) cyclotriphosphazene (TPP) [17,18,19] and 3,3 ,4,4 -tetrakis(trimethylsilylethynyl)biphenyl (TTEB) [20] are well-known for producing MPMs merely as a consequence of frustrated packing, even though they do not have pre-fabricated molecular free volumes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
