Tetranuclear copper(I)-biphenanthroline gridwork: Violation of the principle of maximal donor coordination caused by intercalation and CH-to-N forces

Design principles in polynuclear coordination complexes have been based on the idea that metal ions would acquire donor atoms up to the metal's ligand field preference, and donor ligands, such as 1,10-phenanthroline, would not leave donor atoms uncoordinated to a metal ion. The geometry of the simple molecular grid formed from a series of 3,3′-biphenanthrolines complexed with Cu1 or Ag1 ions set up a cleft that binds uncoordinated ligands through a combination of intercalation, solvation, and CH-to-N interactions (see picture).