Solvent Effects in Thermodynamically Controlled Multicomponent Nanocage Syntheses

Abstract

The solvent effects on the condensation reaction between tetraformylcavitand 2 and ethylene-1,2-diamine 3 are reported. Earlier, it was found that the trifluoroacetic acid-catalyzed condensation of 2 and 2 equiv of 3 in CHCl(3) provides in 82% yield an octahedral nanocage 1 composed of 6 cavitands that are linked together by 12 -CH=N-CH(2)CH(2)-N=CH- linker groups (Liu, X.; Liu, Y.; Li, G.; Warmuth, R. Angew. Chem., Int. Ed. 2006, 45, 901). In tetrahydrofuran, the same reactants yield a tetrameric nanocage 4 (35% yield), which resembles a distorted tetrahedron built up from four cavitands that occupy the apexes. Each cavitand is doubly linked to one other cavitand and singly linked to the other two cavitands via -CH=N-CH(2)CH(2)N=CH- connectors. In CH(2)Cl(2), the reaction between 8 2 and 16 3 yields a square antiprismatic nanocage 5 (65% yield), in which each cavitand occupies one of the eight corners and is connected to four neighboring cavitands via -CH=N-CH(2)CH(2)-N=CH- linkers. Nanocage 5 is also the main product in CH(2)ClCH(2)Cl (26% yield) and CHCl(2)CHCl(2) (33% yield). Reduction of all imine bonds in 4 and 5 yields polyaminonanocontainers 7 and 8, respectively, which were isolated as trifluoroacetate salts. Contrary to the formation of larger capsules composed of four, six, or eight cavitands in the reaction between 2 and 3, the acid-catalyzed reaction of 2 with 2 equiv of H(2)N-X-NH(2) (X = (CH(2))(n)(=3,4,5), 1,3-C(6)H(4), 1,4-(CH(2))(2)C(6)H(4), or 1,3-(CH(2))(2)C(6)H(4)) quantitatively yields octaiminohemicarcerands 9-14, in which two cavitands are connected with four -CH=N-X-N=CH- linkers. The outcomes of these condensation reactions are rationalized with the different diamine structures and the relative orientation of cavitands in 1, 4, 5, and 9-14.

Application of computational methods to the design and characterisation of porous molecular materials

“…115 There are likely limitations to this approach, in particular due to the difficulty of including the effect of solvent choice, 116 which is known to influence topology in some cases. 117 Further, if targeting a specific topology, the accurate quantification of strain or formation energy is challenging for small organic molecules, let alone these, typically large, systems. However, if success levels greater than chemical intuition alone can be achieved, in the future this approach is likely to see success moving beyond the examples of postsynthetic rationalisation to prediction of promising synthetic targets.…”

Facile, high-yielding synthesis of deepened cavitands: a synthetic and theoretical study

“…The obtained tetrakis(methyl)resorcin [4]arene [15] (1) was bridged by BrCH 2 Cl (2), [16] and selectively brominated according to Sorrell and Pigge [17] using azobisisobutyronitrile (AIBN) as a catalyst to afford tetrakis(bromomethyl)cavitand (3) in 80% combined yield. Cavitand 3 was then reacted with an excess of various aliphatic alcohols and phenols in the presence of an adequate base to give the corresponding tetrakis(alkoxymethyl) (5, 6, 10) and tetrakis(aryloxymethyl) cavitands (7)(8)(9) in high (60-78 %) isolated yields. These reactions proceeded well at room temperature; however, full etherification was only seen at 70 °C after 16 hours.…”

“…Recently, dynamic covalent chemistry has been effectively utilized to overcome such difficulties. [7] Self-F o r P e e r R e v i e w O n l y assembly through metal-ligand interactions, van der Waals forces and, mainly, hydrogen bonding also plays an important part in constructing large molecular capsules with increased internal cavities. [8] On the other hand, these non-covalent systems often suffer from relative instability, functional group intolerance and insolubility in organic solvents.…”

A simple one-pot multicomponent synthesis of an octahedral nanocontainer molecule

“…We have carried out this reaction on a half-gram scale and do not find a decrease in the yield of 1 as long as the reactants are of high purity. On the other hand, the condensation reaction is remarkably solvent dependent 35 . In solvents other than chloroform, the yield of 1 is considerably lower and other nanocages form preferentially.…”

“…For a discussion of the solvent effect on the outcome of the condensation reaction between 2 and 3, the reader is referred to ref. 35.…”