Ferrocene-Containing Pseudorotaxanes in Crystals: Aromatic Interactions with Hammett Correlation.

Yuji Suzaki,Kohtaro Osakada,Yugo Fukuchi,Take-Aki Koizumi,Asami Takei,Tomoko Abe,Masaki Horie

doi:10.3390/molecules27051745

Abstract

Single crystals of pseudorotaxanes, [(FcCH2NH2CH2Ar)(DB24C8)][PF6] (DB24C8 = dibenzo[24]crown-8, Fc = Fe(C5H4)(C5H5), Ar = -C6H3-3,4-Cl2, -C6H3-3,4-F2, -C6H4-4-F, -C6H4-4-Cl, -C6H4-4-Br, -C6H3-3-F-4-Me, -C6H4-4-I) and [(FcCH2NH2CH2C6H4-4-Me)(DB24C8)][Ni(dmit)2] (dmit = 1,3-dithiole-2,4,5-dithiolate), were obtained from solutions containing DB24C8 and ferrocenylmethyl(arylmethyl)ammonium. X-ray crystallographic analyses of the pseudorotaxanes revealed that the aryl ring of the axle moiety and the catechol ring of the macrocyclic component were at close centroid distances and parallel or tilted orientation. The structures with parallel aromatic rings showed correlation of the distances between the centroids to Hammett substituent constants of the aryl groups.

Highlights

Rotaxanes and pseudorotaxanes have been investigated as supramolecules with unique structures, having macrocyclic molecules threaded by axle molecules [1–9]
Dibenzo-24-crown-8 (DB24C8) forms various pseudorotaxanes and rotaxanes with dialkyl- or diarylammonium because they are bound by multiple N-H· · · O hydrogen bonds between the NH2+ group and the oxygen atoms
The d and θ values of 1a (3.553 Å and 3.65◦) and of 1j (3.779 Å and 7.94◦) indicate that the C6H3-3,4-Cl2 ring of 1a and the catechol ring of DB24C8 is closer and less tilted than those of the C6H3-4-OMe ring of 1i and the catechol ring of DB24C8 because of stronger donor–acceptor interaction in the former system. Williams, and their co-workers investigated a full series of pseudorotaxanes composed of DB24C8 and bis(arylmethyl)ammonium in the solid state and in solution

Summary

Introduction

Rotaxanes and pseudorotaxanes have been investigated as supramolecules with unique structures, having macrocyclic molecules threaded by axle molecules [1–9]. One of the two crystallographically independent pseudorotaxanes was stabilized by the hydrogen bonds and by π–π interaction between a Ph group of the axle component and a catechol group of the macrocycle. Williams, and their co-workers investigated a full series of pseudorotaxanes composed of DB24C8 and bis(arylmethyl)ammonium in the solid state and in solution They observed a clear relationship between the stability constants for the pseudorotaxane and the electron donating ability of the substituents of the aryl groups of the axle components in CDCl3 and CD3CN-CDCl3 [55]. Higher stability of pseudorotaxanes possessing aryl groups with electron-withdrawing groups, such as NO2 and COOH groups, at the para position can be attributed to the aromatic interaction between the axle and macrocyclic components. Other chemicals are commercially available and used without further purification

Materials and Methods

Crystal Synthesis of [(FcCH2NH2CH2C6H4-4-Cl)(DB24C8)]PF6 (1d)

Crystal Synthesis of [(FcCH2NH2CH2C6H4-4-Me)(DB24C8)][Ni(dmit)2] (1i-Ni)

3.10. X-ray Crystallography Data were collected on a Rigaku

Conclusions