Heterotapes: a persistent, dual-synthon hydrogen-bonding motif

Area of Science:

• Supramolecular Chemistry
• Crystal Engineering
• Coordination Chemistry

Background:

• The carbamoyldicyanomethanide anion ([C(CN)2-(CONH2)]-, cdm) is a small dinitrile anion.
• Hydrogen bonding plays a crucial role in the self-assembly of supramolecular structures.

Purpose of the Study:

• To investigate the self-assembly behavior of the carbamoyldicyanomethanide anion.
• To explore the formation of hydrogen-bonded tapes and their stability in different chemical environments.

Main Methods:

• Synthesis and characterization of the carbamoyldicyanomethanide anion.
• Crystallographic analysis of ion-pair structures and coordination complexes.
• Investigation of hydrogen bonding interactions using structural data.

Main Results:

• The carbamoyldicyanomethanide anion reproducibly forms a hydrogen-bonded tape featuring both an amide dimer and a nitrile-containing ring, termed a "heterotape".
• This heterotape motif demonstrates robustness, persisting in isolated ion-pair structures ([K(15c5)2](cdm) x H2O) and coordination complexes.
• Complexes with octahedral metals and specific coligands (e.g., di(2-pyridyl)amine, cyclam) retain the heterotape, while others (e.g., with ethylene diamine) show alternative motifs due to ligand interference.

Conclusions:

• The carbamoyldicyanomethanide anion is a versatile building block for constructing robust hydrogen-bonded supramolecular architectures.
• The formation of the heterotape motif is influenced by the nature of co-ligands in coordination complexes.
• This study highlights the predictable and adaptable nature of supramolecular synthons in crystal engineering.