Expanded Ligands Based upon Iron(II) Coordination Compounds of Asymmetrical Bis(terpyridine) Domains

The synthesis and characterization of two tritopic ligands containing a 2,2':6',2''-terpyridine (tpy) metal binding domain and either a 3,2':6',3''- or a 4,2':6',4''-tpy domain are detailed. The synthetic routes to these ligands involved the [Pd(dppf)Cl2]-catalyzed coupling of a boronic ester-functionalized 2,2':6',2''-tpy with bromo-derivatives of 3,2':6',3''-tpy or 4,2':6',4''-tpy. The 2,2':6',2''-tpy domains of the tritopic ligands preferentially bind Fe2+ in reactions with iron(II) salts leading to the formation of two homoleptic iron(II) complexes containing two peripheral 3,2':6',3''-tpy or 4,2':6',4''-tpy metal binding sites, respectively. These iron(II) complexes are potentially tetratopic ligands and represent expanded versions of tetra(pyridin-4-yl)pyrazine.

Automated summary

This article describes the synthesis and characterization of two tritopic ligands containing a 2,2':6',2''-terpyridine (tpy) metal binding domain and either a 3,2':6',3''- or a 4,2':6',4''-tpy domain. The synthetic routes involved the [Pd(dppf)Cl2]-catalyzed coupling of a boronic ester-functionalized 2,2':6',2''-tpy with bromo-derivatives of 3,2':6',3''-tpy or 4,2':6',4''-tpy. The tritopic ligands preferentially bind Fe2+ ions and form iron(II) complexes with two peripheral 3,2':6',3''-tpy or 4,2':6',4''-tpy metal binding sites.