Halogen Bonding Interactions in Halopyridine–Iodine Monochloride Complexes

Abstract

Halogen bond interactions are investigated in four halopyridine iodine monochloride complexes nXPy­(N)–ICl in the solid state, solution and in silico, where nXPy = n-halopyridine, X = I or Br and n = 2 or 3. Two types of halogen bonding interactions were observed: stronger three-center Py­(N)–ICl halogen bonds and weaker two-center Py­(C)–X···Cl halogen bonds. Theoretical calculations (thermodynamic data and optimized bond distances) and solution NMR studies indicated that Py­(N)–ICl halogen bonding interactions are stronger in 3XPy­(N)–ICl complexes than in 2XPy­(N)–ICl complexes. In the solid state, relying on bond distances, nBrPy­(N)–ICl complexes show the same behavior to that in solution and in silico. In contrast, nIPy­(N)–ICl halogen bonding interactions are stronger in 2IPy­(N)–ICl than in 3IPy­(N)–ICl. The ionic and covalent characters of I–Cl and N–I bonds were studied by the analysis of electron density topology using Quantum Theory of Atoms in Molecules (QTAIM), and Natural Population Analysis (NPA)/Natural Bond Orbital (NBO) analysis. According to the NBO analysis of the solid state structure, the ionic character of the I–Cl bond is higher in 2IPy­(N)–ICl than in 3IPy­(N)–ICl.

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

“…There is an alternative approach to making a reliable halogen bond donor by placing a halogen atom on a positively charged species. To date, a number of halogenoimidazolium and halogenopyridinum cations employed as halogen bond donors in salts with organic [78,79] and inorganic [13,25,[44][45][46][47][48][49][50][51][52][53][54][80][81][82][83][84][85][86][87][88][89][90][91] counterions have been published. Halogenopyridinium cations have been studied as anion receptors [92][93][94][95][96], catalysts in halogenide abstraction [97], colour tuning [98,99] and as counterions for tuning conductivity and magnetic properties in supramolecular conductors [100][101][102][103].…”

Crystal structure of bis(1,8-dibenzoyl-7-methoxynaphthalen-2-yl)terephthalate: Terephthalate phenylene moiety acts as bidentate hydrogen acceptor of bidirectional C-H···π non-classical hydrogen bonds

“…Indeed, weak interactions have been established as essential features in influencing the chemical, physical, and biological activity properties of materials [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], by determining their threedimensional single molecular structure and spatial organization of molecular assembly. A number of papers and reviews have been dedicated to the crystallographic and theoretical study and consequently the analysis of halogen interactions and nonclassical hydrogen bonds such as C-H•••X (X = Polar atom) and C-H•••π hydrogen bonds have drastically increased over recent years, emphasizing the applicability and usefulness of weak interactions to scientific disciplines [22][23][24][25][26][27][28][29][30].…”

An emerging deep eutectic solvent based on halogen-bonds

“…8 Regrettably, most reported studies were based on crystallography and theoretical calculations, and studies in solution are extremely limited, let alone as a solvent system. 9,10 To date, there have been several reports of XB-based eutectic solvents, but they are all about non-ionic systems, which are not typical DESs. 11,12…”

“…8 Regrettably, most reported studies were based on crystallography and theoretical calculations, and studies in solution are extremely limited, let alone as a solvent system. 9,10 To date, there have been several reports of XB-based eutectic solvents, but they are all about non-ionic systems, which are not typical DESs. 11,12 Among the components of XBs, the halide anions are widely used as acceptors owing to their high polarization, small steric hindrance and multi-coordination numbers.…”

“…9 The dihalogens are good XB donors as well. 10,13 The trihalides, formed by the strong XB interactions between them, have received much attention. 13 Herein, we chose iodine monobromide (IBr) and iodine monochloride (ICl) as representatives to combine with quaternary ammonium salts, obtaining a series of halogenbonded trihalide anion-based DESs (XDESs) by regulating the components and ratios.…”