para-substituted pyridines: Effects on the interaction with 2-perfluoropropyl iodide and vibrations

Fluorescent nano-sized aggregates of halogen bonded complexes formed using perfluoropropyl iodides: a systematic comparison between two isomeric halogen bond acceptors, aniline and 4-methyl pyridine

“…From a previous study, we realised that the formation of XB between MePy and iso-C 3 F 7 I was accompanied by electron density delocalisation from the electron lone pair on N py to the s* bond orbital of C-I, and from the s orbital of C-I bond to the s* orbital of C-F b bond, which contributed to the CT within the XB complex. 10 As a result, the MEP for this system indicated a negative region around F atoms relative to the positive region around the methyl group in the para position. The plot of the MEP mapped over the electron density provides hints concerning the possible aggregation among the XB complexes dominated by electrostatic forces, similarly to the aggregation of ion pairs, [30][31][32][33] which will alter the morphology of the bulk system.…”

“…Structures, thermal stability and RNMs of XB complexes [ANLÁiso-C 3 F 7 I] system. The XBs between MePy and iso-C 3 F 7 I are rather straightforward, wherein, the N py is the only XB acceptor centre, 10 whereas the interaction between ANL and iso-C 3 F 7 I can be more complicated, as both N am and ring C atoms at the para or ortho positions relative to the amino group may be the XB acceptors, not to mention the possible conformations of XB complexes due to the different orientations of C-F a bonds relative to the benzene ring on ANL. In addition, the F atoms on iso-C 3 F 7 I (with negative electrostatic potential) may also interact with ring C atoms (with positive electrostatic potential), e.g.…”

“…The same computational approach as that described in ref. 10 was adopted. In addition, UV-Vis absorption and emission spectra were simulated for the XB complexes, at the TD-DFT CAM-B3LYP 42 6-311++G** (H, C, N, F) and DGDZVP (I) levels.…”

“…12,25 With respect to the impact on the ring related vibrations, it is well established the RNMs, especially RNM 1 , RNM 3 and RNM 7 of pyridine and derivatives are subjected to wavenumber shifts upon XB via N py . 10,26 The formation of XB with amino group on ANL unavoidably affects the p-p conjugation between N am and benzene ring, and consequently the p electron density distribution over the ring. However, it remains unknown whether this change in the ring p electron density may lead to any significant RNM frequency shift.…”

“…The basicity and electron donating ability of MePy are stronger than those of pyridine and ANL, consistent with the descriptor developed to quantify the effects of the electron donating/withdrawing substituents in mono-substituted benzenes and para-substituted pyridines. 10 Moreover, intra-and intermolecular XB involving aromatic N am and N py are gaining increasing attention for their employment in supramolecular design, crystal engineering, catalyst development, halogen related enzymatic mechanisms and pharmaceutical synthesis. [11][12][13][14][15][16][17][18][19][20][21] According to the Cambridge Structure Database, only 10% of the crystal structures involving XB based on perfluoro iodobenzene are C-IÁ Á ÁN (primary amine) types for two main reasons, 22 i.e.…”