Multiple hydrogen-bonded dimers: are only the frontier atoms relevant?

Area of Science:

• * Quantum chemistry
• * Molecular interactions
• * Organic chemistry

Background:

• * Hydrogen-bonded aromatic dimers exhibit significant interaction energy changes due to non-frontier atom exchanges.
• * Understanding these energy changes is crucial for molecular design and predicting chemical behavior.

Purpose of the Study:

• * To investigate the factors governing hydrogen-bond strengths in N-edited guanine-cytosine base pair isosteres.
• * To determine if charge accumulation in monomers can explain observed interaction energy variations.
• * To elucidate the role of non-frontier atoms in modulating hydrogen-bond interactions.

Main Methods:

• * Quantum-chemical analyses were employed to study the electronic structure and interaction energies.
• * Focus was placed on N-edited guanine-cytosine base pair isosteres.
• * Calculations assessed charge distribution and hydrogen-bond strengths.

Main Results:

• * Non-frontier atom exchanges were found to induce substantial changes in interaction energies (up to 6.5 kcal mol^-1).
• * The relative hydrogen-bond strengths of the studied isosteres could not be explained by frontier atom interactions alone.
• * Charge accumulation within the individual monomers was identified as the key factor determining hydrogen-bond strengths.

Conclusions:

• * Charge accumulation in monomers is a critical determinant of hydrogen-bond strength in N-edited guanine-cytosine base pair isosteres.
• * Explanations for interaction energy changes must consider electronic effects beyond frontier atoms.
• * This finding provides new insights into the design and stability of modified nucleobases and related systems.