A Raman Spectroscopic and Computational Study of New Aromatic Pyrimidine-Based Halogen Bond Acceptors

Abstract

Two new aromatic pyrimidine-based derivatives designed specifically for halogen bond directed self-assembly are investigated through a combination of high-resolution Raman spectroscopy, X-ray crystallography, and computational quantum chemistry. The vibrational frequencies of these new molecular building blocks, pyrimidine capped with furan (PrmF) and thiophene (PrmT), are compared to those previously assigned for pyrimidine (Prm). The modifications affect only a select few of the normal modes of Prm, most noticeably its signature ring breathing mode, ν1. Structural analyses afforded by X-ray crystallography, and computed interaction energies from density functional theory computations indicate that, although weak hydrogen bonding (C–H···O or C–H···N interactions) is present in these pyrimidine-based solid-state co-crystals, halogen bonding and π-stacking interactions play more dominant roles in driving their molecular-assembly.

Interrogating the Interplay between Hydrogen and Halogen Bonding in Graphitic Carbon Nitride Building Blocks

“…The reliability of using complexation shifts in the vibrational C–X and CC stretching frequencies as indicators for XB formation is also assessed. Although the magnitude of these shifts is nearly identical to those reported in the literature, the XB complexes studied here are bound more strongly than pyridine- (up to 25%) and pyrimidine-based complexes (up to 4%). , Our results suggest that the XB complexes identified here will lead to highly ordered XB-driven cocrystals, which may find utility as supramolecular architectures for applications like organic optoelectronic devices, gas storage, or chemical transformation substrates.…”

“…This finding is supported by the relatively low barriers of rotation between the XB donors and acceptors known to plague similar XB-driven complexes. 32,38,39 The results of the XB trimers reported in Table 2 tell a story commensurate with those of the dimer complexes. As it turns out, the overall binding energies of the dimers are nearly additive (within 94−98%) with those of the trimers.…”

“…In addition, higher-lying transition state structures exhibiting perpendicular XB angles (i.e., α XB = 90°) that potentially connect the global and local minima on their respective potential energy surfaces were discovered. This finding is supported by the relatively low barriers of rotation between the XB donors and acceptors known to plague similar XB-driven complexes. ,, …”

Probing halogen bonding interactions between heptafluoro-2-iodopropane and three azabenzenes with Raman spectroscopy and density functional theory

“…Nitrogen-containing heterocycles have received much attention in the past as participants in covalent and noncovalent charge transfer interactions. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Additionally, these studies highlight the usefulness of vibrational spectroscopy, particularly Raman spectroscopy, as a probe of noncovalent interactions. Azines and their derivatives have also been studied in halogen-bonded complexes in the past.…”

The Nitrogen Bond, or the Nitrogen-Centered Pnictogen Bond: The Covalently Bound Nitrogen Atom in Molecular Entities and Crystals as a Pnictogen Bond Donor

“…A task group has been charged with categorizing tetrel bonding, pnictogen bonding, and other non-covalent interactions, involving the elements of Groups 14-16 of the periodic table [4]. The proposed characteristics of these bonding interactions have emerged from observations of a variety of engineered chemical systems in the crystalline, liquid and gas phases, and examining signatures arising from IR [5,6], Raman [7,8], UV/vis [9,10], and NMR [10,11] methods, and from ab initio and density functional theory calculations [12][13][14]. The characteristic features vary from system to system because they are dependent on the nature of the electron density distribution associated with the electron donor and electron acceptor fragments driving the non-covalent interactions.…”