Anyfanti Goulielmina, Bauzá Antonio, Gentiluomo Lorenzo, Rodrigues João, Portalone Gustavo, Frontera Antonio, Rissanen Kari, Puttreddy Rakesh
Department of Chemistry, University of Jyvaskyla, Jyvaskyla, Finland.
Centro de Química da Madeira, MMRG, Universidade da Madeira, Funchal, Portugal.
Front Chem. 2021 Apr 29;9:623595. doi: 10.3389/fchem.2021.623595. eCollection 2021.
Hexamethylenetetramine (HMTA) and -haloimides form two types of short (imide)X···N and X-X···N (X = Br, I) halogen bonds. Nucleophilic substitution or ligand-exchange reaction on the peripheral X of X-X···N with the chloride of -chlorosuccinimide lead to Cl-X···N halogen-bonded complexes. The 1:1 complexation of HMTA and ICl manifests the shortest I···N halogen bond [2.272(5) Å] yet reported for an HMTA acceptor. Two halogen-bonded organic frameworks are prepared using 1:4 molar ratio of HMTA and -bromosuccinimide, each with a distinct channel shape, one possessing oval and the other square grid. The variations in channel shapes are due to tridentate and tetradentate (imide)Br···N coordination modes of HMTA. Density Functional Theory (DFT) studies are performed to gain insights into (imide)X···N interaction strengths (ΔE). The calculated ΔE values for (imide)Br···N (-11.2 to -12.5 kcal/mol) are smaller than the values for (imide)I···N (-8.4 to -29.0 kcal/mol). The DFT additivity analysis of (imide)Br···N motifs demonstrates Br···N interaction strength gradually decreasing from 1:1 to 1:3 HMTA:-bromosuccinimide complexes. Exceptionally similar charge density values ρ(r) for N-I covalent bond and I···N non-covalent bond of a (saccharin)N-I···N motif signify the covalent character for I···N halogen bonding.
六亚甲基四胺（HMTA）与卤代酰亚胺形成两种类型的短（酰亚胺）X···N和X-X···N（X = Br、I）卤素键。X-X···N外围X上的亲核取代或配体交换反应与氯代琥珀酰亚胺的氯反应生成Cl-X···N卤素键合配合物。HMTA与ICl的1:1络合表现出迄今报道的HMTA受体最短的I···N卤素键[2.272(5) Å]。使用1:4摩尔比的HMTA和溴代琥珀酰亚胺制备了两种卤素键合有机框架，每种都具有独特的通道形状，一种为椭圆形，另一种为方格形。通道形状的变化归因于HMTA的三齿和四齿（酰亚胺）Br···N配位模式。进行密度泛函理论（DFT）研究以深入了解（酰亚胺）X···N相互作用强度（ΔE）。（酰亚胺）Br···N的计算ΔE值（-11.2至-12.5 kcal/mol）小于（酰亚胺）I···N的值（-8.4至-29.0 kcal/mol）。（酰亚胺）Br···N基序的DFT加和分析表明，从1:1到1:3的HMTA:溴代琥珀酰亚胺配合物中，Br···N相互作用强度逐渐降低。（糖精）N-I···N基序的N-I共价键和I···N非共价键的电荷密度值ρ(r)异常相似，表明I···N卤素键具有共价特征。
