Substituent effect on supramolecular motifs in series of succinimide polycyclic keto derivatives – Spectroscopic, theoretical and crystallographic studies

Abstract

The substituent effect on the supramolecular arrangement in a series of polycyclic monoimide keto derivatives crystals was studied. Single crystal X-ray diffraction and IR spectroscopic experiments were performed for seven related compounds, as well as the Hirshfeld surface analysis and quantum chemical calculations at HF and DFT levels in vacuo, in solution and for small clusters. The presence of CO group at the bridge of the main hydrocarbon skeleton implied the catemer motif of the NimideH⋯Oimide hydrogen bond in case of smaller substituents (H, MeO, EtO). For more voluminous groups (iBuO) or additional hydrogen bond acceptors (AcO, O) the steric hindrance increased and the imide⋯imide interactions were no longer present in the solid state. The NimideH⋯Oketo or NimideH⋯Oester hydrogen bonds were formed instead. The binding energy per one NH⋯O interaction calculated for supramolecular clusters at HF/6-31G(d,p) level was ca. 20kJmol−1, indicating moderate strength of this hydrogen bond. The solvation free energies and induced dipole moments were computed at B3LYP/6-311+G(d,p) level using the integral equation formalism model (IEF PCM) considering three solvents of various polarity: non-polar chloroform, polar aprotic dimethyl sulfoxide (DMSO) and polar protic water. The relations between the vibrational spectra and the crystal structure have been discussed. The following sequence of carbonyl stretching modes in IR spectra has been derived from quantum chemical calculations: (1) at the highest frequencies – the symmetric vibration of two imide CO bonds, (2) the vibrations of keto CO bonds attached directly to the polycyclic hydrocarbon skeleton, (3) the asymmetric vibration of two imide CO bonds, and (4) at the lowest frequencies – the vibration of ester CO group. The characteristic peaks observed in imide experimental IR spectra at about 3080cm−1 have been explained as overtone and combination bands of νCO stretching and γNH out-of-plane bending vibrations.