Multiphoton Ionization and Dissociation of Diazirine: A Theoretical and Experimental Study

Energy Landscape and Structural and Spectroscopic Characterization of Diazirine and Its Cyclic Isomers

Identifying new nitrogenated hydrocarbon molecules in the interstellar medium (ISM) is challenging because of the lack of comprehensive spectroscopic data from experiments. In this computational work, we focus on investigating the structures, relative energies, spectroscopic constants, and energy landscape of the cyclic isomers of diazirine (c-CH2N2) using ab initio quantum chemical methods. Density functional theory (DFT) methods and coupled cluster theory with singles and doubles including perturbative triples [CCSD(T)] and CCSD(T) with the explicitly correlated F12b correction [CCSD(T)-F12b] were employed for this purpose along with large correlation consistent cc-pVTZ, cc-pVQZ, and cc-pV5Z basis sets. Harmonic vibrational frequencies, infrared vibrational intensities, rotational constants, and dipole moments are reported. Anharmonic vibrational fundamentals along with centrifugal distortion constants, and vibration-rotation interaction constants are also reported for all the cyclic isomers. The energies computed with the CCSD(T) and CCSD(T)-F12b methods were extrapolated to the one-particle complete basis set (CBS) limit following a three-point formula. At the CCSD(T)-F12b/CBS level of theory, the 3,3H-diazirine (c-CH2N2) is the lowest energy cyclic isomer followed by 1,3H-diazirine, (E)-1,2H-diazirine, and (Z)-1,2H-diazirine, which are 20.1, 47.8, and 51.3 kcal mol-1 above the 3,3H-diazirine, respectively. Accurate structures and spectroscopic constants that are reported here could be useful for future identification of these cyclic nitrogenated organic molecules in the interstellar medium or circumstellar disks.

Structure, Bonding, and Photoaffinity Labeling Applications of Dialkyldiazirines

Dialkyldiazirine photoaffinity probes are unparalleled tools for the study of small molecule–protein interactions. Here we summarize the basic principles of structure, bonding, and photoreactivity of dialkyldiazirines, current methods for their synthesis, and their practical application in photoaffinity labeling experiments. We demonstrate the unique utility of dialkyldiazirine probes in the context of our recent photoaffinity crosslinking-mass spectrometry analysis to reveal a hidden cholesterol binding site in the Hedgehog morphogen proteins.

1 Introduction

2 Structure, Bonding, and Spectral Properties

3 Photoreactivity

4 Synthesis

5 Application in Photoaffinity Labeling

6 Discovery of a Cholesterol–Hedgehog Protein Interface

7 Conclusions and Outlook

Theoretical study of non-Hammett vs. Hammett behaviour in the thermolysis and photolysis of arylchlorodiazirines

Calculations show that the different Hammett behaviour of arylchlorodiazirines is due to different mechanisms in the ground and excited state.

Dynamic Symmetry Breaking Hidden in Fano Resonance of a Molecule: S1 State of Diazirine Using Quantum Wave Packet Propagation

Fano resonance in the predissociation of the S1 state of diazirine was studied by applying a time-dependent wave packet propagation method, and dynamic symmetry breaking (DSB) around the stationary structure of S1 was disclosed in a detailed analysis of this theoretical result. The DSB was found to originate in coupling between the asymmetric C-N2 stretching and CH2 wagging modes, suggesting that there is a slight time gap between ring opening and the concurrent dragging of two H atoms of the CH2 moiety. Although the depth of the double well due to DSB is just 0.011 eV, its presence noticeably affects the early time dynamics and observed spectrum.

Experimental and computational study of solvent effects on one- and two-photon absorption spectra of chlorinated harmines

We present a combined experimental and computational study of one- and two-photon absorption spectra of protonated chloroharmines in aqueous and acetonitrile solutions.