Shedding Light on the Vibrational Signatures in Halogen‐Bonded Graphitic Carbon Nitride Building Blocks

Abstract

The relative contributions of halogen and hydrogen bonding to the interaction between graphitic carbon nitride monomers and halogen bond (XB) donors containing CÀ X and C�C bonds were evaluated using computational vibrational spectroscopy. Conventional probes into select vibrational stretching frequencies can often lead to disconnected results. To elucidate this behavior, local mode analyses were performed on the XB donors and complexes identified previously at the M06-2X/ aVDZ-PP level of theory. Due to coupling between low and high energy CÀ X vibrations, the C�C stretch is deemed a better candidate when analyzing XB complex properties or detecting XB formation. The local force constants support this conclusion, as the C�C values correlate much better with the σ-hole magnitude than their CÀ X counterparts. The intermolecular local stretching force constants were also assessed, and it was found that attractive forces other than halogen bonding play a supporting role in complex formation.

Elucidating the Role of Electron-Donating Groups in Halogen Bonding

“…These interactions promote further polarization of the halogen atom, generating a more positive V S,max and larger E bind compared to EDGs in the meta or para positions. The side interactions, known as hydrogen bond-enhanced halogen bonds (HBeXB), have been reported to improve the interaction strength and stability of XB complexes in the literature. − ,,, The BH 2 substituent is the exception to this trend. When at the ortho position, it yields the smallest V S,max and weakest E bind compared to meta or para positions that are comparable.…”

“…This electronegative region can behave as a Lewis base forming hydrogen bond (HB) or XB interactions. These additional interactions with the electronegative belt have been shown recently to enhance the strength of the XBs in complexes. − …”

“…The side interactions, known as hydrogen bond-enhanced halogen bonds (HBeXB), have been reported to improve the interaction strength and stability of XB complexes in the literature. [22][23][24][25][26][27]29,30,71 The BH 2 substituent is the exception to this trend. When at the ortho position, it yields the smallest V S,max and weakest E bind compared to meta or para positions that are comparable.…”