Halogen Bonding between an Isoindoline Nitroxide and 1,4‐Diiodotetrafluorobenzene: New Tools and Tectons for Self‐Assembling Organic Spin Systems

Abstract

Radical assembly: Halogen bonding has been observed for the first time between an isoindoline nitroxide and an iodoperfluorocarbon (see figure), which cocrystallize to form a discrete 2:1 supramolecular compound in which N--O(.)I halogen bonding is the dominant intermolecular interaction. This illustrates the potential use of halogen bonding and isoindoline nitroxide tectons for the assembly of organic spin systems.The isoindoline nitroxide 1,1,3,3-tetramethylisoindolin-2-yloxyl (TMIO) and 1,4-diiodotetrafluorobenzene readily form a discrete 2:1 complex that shows evidence of relatively strong N--O(.)I halogen bonding. This interaction was characterized in the solid state by single-crystal X-ray analysis, thermal analysis, and vibrational spectroscopy (IR and Raman), backed by density functional theory calculations. EPR spectroscopy performed on a solution of TMIO in pentafluoroiodobenzene, a halogen-bonding donor, indicates that halogen bonding induces an increase in electron density at the nitroxide nitrogen nucleus and an increase in the nitroxide rotational correlation time. Our findings demonstrate the potential of utilizing halogen-bonding interactions to promote the self-assembly of new isoindoline nitroxide tectons for the preparation of organic spin systems.

Magnitude and Origin of the Attraction and Directionality of the Halogen Bonds of the Complexes of C6F5X and C6H5X (X=I, Br, Cl and F) with Pyridine

“…[33][34][35][36][37][38][39][40][41] The NMR and other spectroscopic measurements of halogen bonds have also been reported. [29,[43][44][45][46][47][48] The electron density around the halogen atoms has been studied by ab initio molecular orbital calculations. [52][53][54][55][56][57][58][59] Symmetry-adapted perturbation theory (SAPT), atoms-in-molecules (AIM) and natural bond orbital (NBO) calculations were applied to elucidate the nature of halogen bonds.…”

Organizing Radical Species in the Solid State with Halogen Bonding

“…15a) [59]. This work was extended by Micallef to isoindoline nitroxide [60,61]: a similar trimeric entity was crystallized (Fig. 15b) while EPR spectroscopy performed in solution with pentafluoroiodobenzene indicated that halogen bonding induces an increase in electron density at the nitroxide nitrogen nucleus and an increase in the nitroxide rotational correlation time.…”

Halogen Bonding in Crystal Engineering

“…Optimizing the electrostatic and charge transfer aspects have been successfully used in designing of drugs, liquid crystals, organic semiconductors, magnetic materials, nonlinear optical materials, and templates for solid synthesis. [12][13][14][15][16] Conventionally, halogen bonds have been divided into two classes, TypeI and Type II (Fig. 3), based solely on the bonding geometry.…”