Related Experiment Video
Updated: May 15, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Theoretical Study of the Effect of Cis-Trans Isomerism on 1,2-Dihaloethylene-Formic Acid Complexes
1Department of Chemistry, Faculty of Science, Ilam University, Ilam 69315-516, Iran.
Abstract:
This study employs MP2/aug-cc-pVTZ(PP) calculations to examine the influence of geometric isomerism on the noncovalent interaction (NCI) patterns in complexes formed between formic acid (FA) and the cis and trans isomers of 1,2-dihaloethylene (1,2-DHE-C2H2X2). Four stable complexes were identified, each exhibiting distinct structural characteristics. Complexes involving the trans isomers are stabilized exclusively through cyclic, double hydrogen-bonding (HB-HB) interactions. In contrast, the cis isomers form structures stabilized by a cooperative triad of hydrogen- and halogen-bonding interactions (HB-XB-HB). Interaction energy analyses indicate that the trans complexes are, overall, the most stable among the identified structures. Although energy decomposition analysis (EDA) confirms that electrostatic interactions constitute the dominant contribution to the stabilization of all complexes, complementary analyses reveal that specific orbital-driven charge-transfer interactions particularly lp(X) → σ* (O-H) play a crucial role in stabilizing the cooperative HB-XB-HB networks formed by the cis isomers.
Related Concept Videos
Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Disubstituted Cyclohexanes: cis-trans Isomerism
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
Stereoisomerism of Cyclic Compounds
Stability of Conjugated Dienes
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
Stability of Substituted Cyclohexanes
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...

