Cross‐Conjugated π‐Scaffolding with Pendant N‐Heterocyclic Metal‐Binding Sites

• Published in: European journal of organic chemistry 2017-06, Vol.2017 (21), p.3101-3106
• Main Authors: Nauroozi, Djawed, Bruhn, Clemens, Faust, Rüdiger
• Format: Article
• Language: English
• Subjects: Alkynes; Cross‐conjugation; Enediynes; Molecular wires; N ligands; Nitrogen heterocycles
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201700294

The synthesis of geminal enediyne scaffolds with pendant N‐heterocyclic metal‐coordination sites based on dipyridylmethylidene or diazafluorenylidene moieties are reported. The Pd‐catalysed cross‐coupling reactions of the corresponding heterocyclic dibromoolefins and terminal alkynes provide convenient access to the new ligand systems. Their photophysical and electrochemical properties are investigated by UV/Vis spectroscopy and cyclic voltammetry and reveal a more efficient π delocalisation in the cross‐conjugated diazafluorenylidene systems. The coordination of a PdCl2 fragment to each of the different ligand types along with a comprehensive X‐ray crystallographic analysis of the ligands and complexes is reported. The structural data confirm the almost coplanar arrangement of the N‐heterocyclic metal binding site and the cross‐conjugated π‐delocalised enediyne scaffold as a prerequisite for efficient electronic communication between the two molecular constituents. Cross‐conjugated geminal enediyne scaffolds with pendant N‐heterocyclic metal‐coordination sites based on dipyridylmethylidene or diazafluorenylidene moieties are reported and structurally characterised along with their PdCl2 complexes.