Synthesis and structure of azole-fused indeno[2,1-c]quinolines and their anti-mycobacterial properties †

Prompted by our discovery of a new class of conformationally-locked indeno[2,1-c]quinolines as anti-mycobacterials, compounds 2a and 3a

Multiple Core and Vibronic Coupling Effects in Attosecond Stimulated X-Ray Raman Spectroscopy

Attosecond Stimulated X-ray Raman Spectroscopy (SXRS) is a promising technique for investigating molecular electronic structure and photochemical processes with high spatial and temporal resolution. We present a theoretical study of SXRS from multiple core excitation sites of the same element. Two issues are addressed: interference between pathways contributing the signals from different sites; and how nuclear vibrations influence the signals. Taking furan as a model system, which contains two types of carbons Cα and Cβ, we performed time-dependent density functional theory calculations and computed the SXRS signals with two pulses tuned at the carbon K-edge. Our simulations demonstrate that the SXRS signal from the Cα and Cβ sites are non-additive, owing to the significant mixed contributions (Cα 1s excitations by the pump pulse followed by Cβ 1s excitations by the probe, or vice verse). Harmonic vibrations linearly coupled to the electronic transitions are incorporated using the cumulant expansion. The nuclei act as a bath for electronic transitions which accelerate the decay of time-domain signal. The frequency-domain spectrum is modified by a small red shift and high-resolution fine-structure features are introduced

Near-Edge X-ray Absorption Spectra of Carbon-Nitride Molecules and Solids

Near-edge x-ray absorption fine structure spectra have been calculated for different carbon-nitrogen molecules, clusters and solids. The compounds investigated are used to model the chemical bonding in carbon nitride thin films. The molecular and cluster spectra are calculated employing the static exchange ab initio technique, while the solid state calculations are performed with the density functional full potential augmented plane wave method

A repertoire of pyridinium-phenyl-methyl cross-talk through a cascade of intramolecular electrostatic interactions

Direct intramolecular cation−π interaction between phenyl and pyridinium moieties in 1a+ has been experimentally evidenced through pH-dependent 1H NMR titration. The basicity of the pyridinyl group (pKa 2.9) in 1a can be measured both from the pH-dependent chemical shifts of the pyridinyl protons as well as from the protons of the neighboring phenyl and methyl groups as a result of electrostatic interaction between the phenyl and the pyridinium ion in 1a+ at the ground state. The net result of this nearest neighbor electrostatic interaction is that the pyridinium moiety in 1a becomes more basic (pKa 2.92) compared to that in the standard 2a (pKa 2.56) as a consequence of edge-to-face cation (pyridinium)−π (phenyl) interaction, giving a free energy of stabilization (ΔΔ ) of −2.1 kJ mol-1. The fact that the pH-dependent downfield shifts of the phenyl and methyl protons give the pKa of the pyridine moiety of 1a also suggests that the nearest neighbor cation (pyridinium)−π (phenyl) interaction also steers the CH (methyl)−π (phenyl) interaction in tandem. This means that the whole pyridine−phenyl−methyl system in 1a+ is electronically coupled at the ground state, cross-modulating the physicochemical property of the next neighbor by using the electrostatics as the engine, and the origin of this electrostatics is a far away point in the moleculethe pyridinyl-nitrogen. The relative chemical shift changes and the pKa differences show that the cation (pyridinium)−π (phenyl) interaction is indeed more stable (ΔΔ = −2.1 kJ mol-1) than that of the CH (methyl)−π (phenyl) interaction (ΔΔ = −0.8 kJ mol-1). Since the pKa of the pyridine moiety in 1a is also obtained through the pH-dependent shifts of both phenyl and methyl protons, it suggests that the net electrostatic mediated charge transfer from the phenyl to the pyridinium and its effect on the CH (methyl)-π (phenyl) interaction corresponds to Δ of the pyridinium ion (∼17.5 kJ mol-1), which means that the aromatic characters of the phenyl and the pyridinium rings in 1a+ have been cross-modulated owing to the edge-to-face interaction proportional to this Δ change