Halogen bonding and isostructurality in 2,4,6‐tris(2‐halophenoxy)‐1,3,5‐triazines

Crystal structures of 2,4,6‐tris(2‐halophenoxy)‐1,3,5‐triazines (halo = fluoro, chloro, bromo, iodo; 2‐XPOT) are discussed in the background of 3‐halophenoxy (3‐XPOT) and 4‐halophenoxy (4‐XPOT) structures. Among inter‐halogen interactions, the electrostatic L‐shaped type II interactions are generally shorter than the inversion‐related type I geometry in 2‐halo compounds. π‐Stacking of triazine rings at van der Waals separation (∼3.5 Å) makes the well‐known Piedfort Unit assembly and the halogen atoms form a trimer motif. 2‐FPOT and 2‐ClPOT are 2D isostructural but there are differences in the complete 3D molecular packing. 2‐BrPOT and 2‐IPOT are a 3D isostructural pair and their isomorphous unit cells have a similarity index of 0.008. The position of the halogen atom causes structural differences in 2‐, 3‐, and 4‐XPOT compounds, with the para‐series showing guest inclusion and the ortho‐ and meta‐compounds having single‐component close‐packed structures. The Cambridge Structural Database is analyzed for structural mimicry upon halogen GRoup eXchange (GRX). Chloro‐, bromo‐, and iodo‐substituted compounds of the same molecule (56 clusters) are isostructural in 30% cases, Cl/Br are identical in 66% pairs, and Br/I in 50% examples of the subdatabase.