A Robust Supramolecular Heterosynthon Assembled by a Hydrogen Bond and a Chalcogen Bond

Linjie Shan,Weizhou Wang,Jian-Ge Wang,Yunfan Zhang,Shaobin Miao,Yu Zhang,Mingyuan Xu

doi:10.3390/cryst11111309

Abstract

The 1:1 and 2:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole have been successfully synthesized and resolved; the noncovalent interactions in the crystal structures have been studied in detail by quantum chemical calculations. In both of the crystal structures, isophthalic acid and 2,1,3-benzoselenadiazole are bound together by a cyclic supramolecular heterosynthon assembled by an O–H···N hydrogen bond and a N–Se···O chalcogen bond. The crystal structures of the 1:1 and 2:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole and the crystal structure of pure isophthalic acid are very similar, which indicates that the [COOH]···[Se−N] cyclic heterosynthon can be an effective alternative to the strong [COOH]2 cyclic homosynthon. The quantum theory of atoms in molecules further recognizes the existence of the hydrogen bond and chalcogen bond. The results of quantum chemical calculations show that the strengths of the π···π stacking interactions in the 1:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole are almost the same as those in the 2:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole, and the strengths of the [COOH]···[Se−N] cyclic heterosynthons (about 9.00 kcal/mol) are less than the strengths of the much stronger [COOH]2 cyclic homosynthons (14.00 kcal/mol). These calculated results are in good agreement with those experimentally observed, demonstrating that, although not as strong as the [COOH]2 cyclic homosynthon, the [COOH]···[Se−N] cyclic heterosynthon can also play a key role in the crystal growth and design.

Highlights

The concept of supramolecular synthon has been generally accepted and widely used in the field of crystal engineering [1,2]
We investigated the structures and properties of the [COOH]···[Se−N] cyclic heterosynthons formed between isophthalic acid and 2,1,3-benzoselenadiazole
Using the same experimental method, we tried to synthesize the cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole with 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 and 1:9 molar ratios

Summary

Introduction

The concept of supramolecular synthon has been generally accepted and widely used in the field of crystal engineering [1,2]. The supramolecular synthons are always assembled with strong or weak hydrogen bonds. The [COOH]2 cyclic homosynthon I in Figure 1 is one of the most common supramolecular synthons in the Cambridge Structural. In the cornerstone paper of Desiraju [1], the first supramolecular synthon discussed is the [COOH]2 cyclic homosynthon I. The other σ-hole bonds can form cyclic homosynthon. Let us add here that, in recent years, many new types of noncovalent bonds have been uncovered and generally accepted by the chemical community [9]. Two N–Se···N chalcogen bonds form a four-membered [Se−N]2 cyclic homosynthon II.

Methods

Results

Conclusion