Spacer length dependent architectural diversity in bis-dipyrrin copper(ii) complexes

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• Bis-dipyrrin ligands offer versatile platforms for constructing metal complexes.
• Tuning ligand structure, particularly spacer length, is crucial for controlling complex architecture and properties.

Purpose of the Study:

• To synthesize and characterize a series of copper(II) complexes with varying bis-dipyrrin ligand spacer lengths.
• To investigate the impact of ligand spacer length on the structural diversity, geometry, and conformation of copper(II) complexes.

Main Methods:

• Synthesis of copper(II) and nickel(II) complexes.
• Extensive characterization using spectroscopic techniques (ESI-MS, IR, NMR, UV/vis, EPR).
• Structural determination via X-ray single crystal analysis and computational studies (DFT).

Main Results:

• Ligand spacer length determined complex nuclearity: n ≤ 6 yielded binuclear complexes (1-5), while n ≥ 7 yielded mononuclear complexes (6-9).
• Copper(II) centers exhibited distorted square planar geometries in binuclear complexes and distorted tetrahedral geometries in mononuclear complexes.
• DFT studies supported structural differences based on odd/even methylene spacers, and syn-/anti-conformations were correlated with spacer length.

Conclusions:

• Spacer length in bis-dipyrrin ligands is a key determinant of copper(II) complex nuclearity and geometry.
• The study establishes a clear relationship between ligand structure and the resulting coordination environment around the copper(II) ion.
• These findings contribute to the understanding of structure-property relationships in coordination chemistry.