Theoretical investigation of intramolecular π-type hydrogen bonding and internal rotation of 2-cyclopropen-1-ol, 2-cyclopropen-1-thiol and 2-cyclopropen-1-amine

Synergy Effects in Heavy Metal Ion Chelation with Aryl- and Aroyl-Substituted Thiourea Derivatives

Detection and removal of metal ion contaminants have attracted great interest due to the health risks that they represent for humans and wildlife. Among the proposed compounds developed for these purposes, thiourea derivatives have been shown as quite efficient chelating agents of metal cations and have been proposed for heavy metal ion removal and for components of high-selectivity sensors. Understanding the nature of metal-ionophore activity for these compounds is thus of high relevance. We present a theoretical study on the interaction between substituted thioureas and metal cations, namely, Cd²⁺, Hg²⁺, and Pb²⁺. Two substituent groups have been chosen: 2-furoyl and m-trifluoromethylphenyl. Combining density functional theory simulations with wave function analysis techniques, we study the nature of the metal-thiourea interaction and characterize the bonding properties. Here, it is shown how the N,N'-disubstituted derivative has a strong affinity for Hg²⁺, through cation-hydrogen interactions, due to its greater oxidizing capacity.

Spectroscopic and Theoretical Study of the Intramolecular π-Type Hydrogen Bonding and Conformations of 2-Cyclopenten-1-ol

The conformations of 2-cyclopenten-1-ol (2CPOL) have been investigated by high-level theoretical computations and infrared spectroscopy. The six conformational minima correspond to specific values of the ring-puckering and OH internal rotation coordinates. The conformation with the lowest energy possesses intramolecular π-type hydrogen bonding. A second conformer with weaker hydrogen bonding has somewhat higher energy. Ab initio coupled-cluster theory with single and double excitations (CCSD) was used with the cc-pVTZ (triple-ζ) basis set to calculate the two-dimensional potential energy surface (PES) governing the conformational dynamics along the ring-puckering and internal rotation coordinates. The two conformers with the hydrogen bonding lie about 300 cm⁻¹ (0.8 kcal/mole) lower in energy than the other four conformers. The lowest energy conformation has a calculated distance of 2.68 Å from the hydrogen atom on the OH group to the middle of the C=C double bond. For the other conformers, this distance is at least 0.3 Å longer. The infrared spectrum in the O-H stretching region agrees well with the predicted frequency differences between the conformers and shows the conformers with the hydrogen bonding to have the lowest values. The infrared spectra in other regions arise mostly from the two hydrogen-bonded species.

Spectroscopic and Theoretical Study of the Intramolecular π-Type Hydrogen Bonding and Conformations of 3-Cyclopentene-1-amine

The infrared and Raman spectra of 3-cyclopentene-1-amine (3CPAM) have been recorded and analyzed, and the experimental investigations have been complemented by theoretical calculations. Ab initio coupled cluster theory with single and double excitations (CCSD) was used with the cc-pVTZ (triple-ζ) basis set to calculate the conformational energy and geometrical parameters for each of the six conformers of this molecule. MP2/cc-pVTZ and B3LYP/cc-pVTZ computations were utilized to calculate the vibrational frequencies of the conformers. Both the spectra and theoretical calculations verify the presence of the conformers and show that the conformer at the lowest energy has intramolecular π-type hydrogen bonding involving the NH₂ group. The hydrogen bonded conformer is about 2 kJ/mol lower in energy than the other conformers. The potential energy topographical contour map for the ring-puckering and NH₂ internal rotation coordinates has been calculated, and this shows how the different conformers can interconvert into each other. The far-infrared spectrum in the 190 to 280 cm^-1 region shows several NH₂ internal rotation bands for each of the different conformers, and these are consistent with one-dimensional representations for their torsional motions.