A One-Dimensional Phase-Modulated (PM) NMR Experiment for Differentiating Spin Systems in Small Molecules Mixtures: With Application to Chiral Discrimination and Bicomponent Organic Systems.

A one-dimensional phase-modulated NMR experiment, which distinguishes the partially resolved peaks and accelerates the data acquisition due to reduced dimensionality, is reported for differentiating spin systems, with application to chiral discrimination. The multifarious utility of the technique is demonstrated in plenteous examples.

Synthesis and Emergent Photophysical Properties of Diketopyrrolopyrrole-Based Supramolecular Self-Assembly.

Diketopyrrolopyrrole (DPP)-based molecular semiconductors exhibit intriguing optical and charge transport properties. Herein, we rationally design a series of electronically identical but structurally distinct Hamilton receptor (HR)-based supramolecular assembly of DPP. The HR endows supramolecular assemblies via hydrogen bonding with enhanced structural ordering and excitonic couplings. The mechanism of supramolecular self-assembly was probed by diffusion ordered spectroscopy (DOSY) nuclear magnetic resonance (NMR) and solid-state IR spectroscopy studies. We investigated the morphology of self-assembly, photophysical and electrochemical properties and compared them with the identical DPP molecular structures without HRs. The microstructure of self-assembly was probed with atomic force microscopy in thin films. Subsequently, the influence of solid-state packing was studied by single-crystal X-ray diffraction. The single-crystal structure of HR-TDPP-C20 reveals slipped stack arrangements between the two neighboring chromophores with π-π stacking distance and slip angle of 3.55 Å and 35.4°, respectively. Notably, the slight torsional angle of 1° between thiophene and lactam rings and small π-π stacking distance suggest a significant intermolecular coupling between thiophene (D) and lactam (A) rings. This intramolecular coupling between two π-π chromophore stacks manifests in their optical properties. In this manuscript, we report rational design and synthesis of supramolecular self-assembly of DPP with a collection of compelling structural and optical properties.

Retention of strong intramolecular hydrogen bonds in high polarity solvents in binaphthalene-benzamide derivatives: extensive NMR studies.

Advanced multidimensional NMR techniques have been employed to investigate the intramolecular hydrogen bonds (HBs) in a series of N,N'-([1,1'-binaphthalene]-2,2'-diyl)bis(benzamide) derivatives, with the site-specific substitution of different functional groups. The existence of intramolecular HBs and the elimination of any molecular aggregation and possible intermolecular HBs are ascertained by various experimental NMR techniques, including solvent polarity dependent modifications of HB strengths. In the fluorine substituted derivative, direct evidence for the engagement of organic fluorine in HB is obtained by the detection of heteronuclear through-space correlation and the coupling between two NMR active nuclei where the transmission of spin polarization is mediated through HBs (1h J FH). The extent of reduction in the strength of 1h J FH on dilution with high polarity solvents directly provided the qualitative measure of HB strength. The HB, although becoming weakened, does not get nullified even in pure high polarity solvent, which is attributed to the structural constraints. The rate of exchange of a labile hydrogen atom with the deuterium of the solvent permitted the measurement of their half-lives, that are correlated to the relative strengths of HBs. The experimental NMR findings are further validated by XRD and DFT-based theoretical computations, such as, NCI and QTAIM.