Isocyanides Versus Nitriles: Divergent Hydrogen Bonding Behavior Driven by the Balance Between Dispersive and...

Area of Science:

• Physical chemistry
• Molecular spectroscopy
• Supramolecular chemistry

Background:

• Hydrogen bonding is crucial in molecular interactions.
• Isocyanides are typically considered poor hydrogen-bond acceptors.
• Understanding noncovalent interactions is key to molecular recognition.

Purpose of the Study:

• To investigate isocyanides as hydrogen-bond acceptors for the first time.
• To characterize the hydrogen-bonded structures of tert-butyl isocyanide (t-BuNC) and pivalonitrile (t-BuCN) with H2O and tert-butyl alcohol (t-BuOH).
• To elucidate the role of dispersive and electrostatic interactions in noncovalent binding.

Main Methods:

• Jet-cooled Fourier transform infrared (FTIR) spectroscopy.
• Analysis of hydrogen-bonded complexes formed between isocyanides and alcohol/water molecules.
• Computational analysis of intermolecular interactions.

Main Results:

• Isocyanides can act as effective hydrogen-bond acceptors.
• Tert-butyl isocyanide (t-BuNC) forms a classical σ-type hydrogen bond with water.
• Pivalonitrile (t-BuCN) forms a dispersion-stabilized orthogonal π-type hydrogen bond with water.
• Replacing water with tert-butyl alcohol enhances dispersion interactions, favoring π-type binding for both molecules.

Conclusions:

• Isocyanide functional groups exhibit versatile hydrogen-bonding capabilities.
• The balance between dispersive and electrostatic forces dictates binding preferences.
• These findings advance the understanding of noncovalent interactions in molecular systems.