Related Experiment Video
Updated: Jul 2, 2026

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines
Published on: June 23, 2019
A simulation of the photoelectron spectrum of pyrazolide
Michael S Schuurman1, David R Yarkony
1Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Abstract:
Building on previous theoretical and spectroscopic studies of the pyrazolyl radical, a new three-state quasidiabatic Hamiltonian is reported which reproduces not only the equilibrium geometries and harmonic frequencies of the nominal X (2)A(2) state and low-lying A (2)B(1) excited state, but also the minimum energy points on the lowest two-state (X (2)A(2), A (2)B(1)) and three-state (X (2)A(2), A (2)B(1), B (2)B(2)) seams of conical intersection. The three-state Hamiltonian includes all terms through second order in both the diagonal and off-diagonal blocks. Its construction is accomplished in two steps. First, a nascent Hamiltonian, centered at the lowest energy two-state conical intersection, is determined using ab initio gradients and derivative couplings. Then, the nascent Hamiltonian is improved by optimizing selected contributions to the second-order coefficients to better reproduce relevant minima and harmonic frequencies. This Hamiltonian is then expressed in a basis tailored to describe the neutral states of interest under the multimode vibronic coupling approximation. The vibronic Hamiltonian is diagonalized to obtain negative ion photoelectron spectra for pyrazolide-h(3) and the completely deuterated analog pyrazolide-d(3). The resultant spectra, determined employing vibronic Hamiltonians as large as 500 million terms, compare favorably to recent theoretical and spectroscopic results for pyrazolyl-d(3) and to spectroscopic results for pyrazolyl-h(3), for which no reliable simulations had been available.
More Related Videos
08:54Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid
Published on: January 25, 2020
14:11Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Related Concept Videos
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
UV–Vis Spectroscopy: Molecular Electronic Transitions
UV–Vis Spectroscopy of Conjugated Systems
One of the factors influencing λmax is the extent of conjugation in the...
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
According to Hooke's law, the vibrational frequency is directly proportional to the...
NMR Spectroscopy of Benzene Derivatives