A novel Eu3+ complex (EuL) based on 1,10-phenanthroline-2-carboxylic was successfully synthesized, and gave a characteristic red emission. The complex was shown to act as a selective luminescence quencher for Fe3+, as shown by the “on/off” switch phenomenon. The quenching curve showed a double-exponential well decay with the increase of Fe3+ ions. The stability constant of EuL/Fe3+ was calculated as 8.6 × 103 L mol−1(lg β/L mol−1 = 3.93). The response showed high selectivity for Fe3+ compared with other metal ions; the complex therefore has the potential to be applied as a fluorescent sensor for Fe3+.Graphical abstractHighlights► A novel Fe3+ luminescent “on–off” sensor is developed based on a Eu3+ complex. ► A 1:1 binding model between the Eu3+ complex and the Fe3+ ion is proposed. ► The binding constant of EuL/Fe3+ is 8.6 × 103 L mol−1(lg β/L mol−1 = 3.93).

Reaction of dilithium derivatives of N,N’-(dimethylsilanediyl)diamines, Me2Si[N(Li)R]2 with benzonitrile followed by treatment with Me2SiCl2 afforded 1,3-bis[1-(N-R-imino)-1-phenylmethyl]-1,3,2,4-diazadisiletidines, the neutral four-membered bissilylene-linked bisamidines, whose structure was established by X-ray diffraction.

A practical synthetic pathway to alkyl-ended ansa-bis(amidinate) ligands was developed via linking the freshly prepared aliphatic group substituted lithium amidinate and the subsequent deprotonation. The lithium complexes prepared by this method were characterized by NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis.

The mononuclear silyl-linked bis(amidinate) titanium compound 2 was prepared by salt metathesis of 1 and TiCl4(thf)2. Alkylation of 2 with methyllithium gave analogue 3. Both 2 and 3 exhibited a configuration similar to ansa-metallocene and showed good activity towards ethylene polymerization after activation with MAO.

The mononuclear silyl-linked bis(amidinate) titanium compound 2 was prepared by salt metathesis of 1 and TiCl4(thf)2. Alkylation of 2 with methyllithium gave analogue 3. Both 2 and 3 exhibited a configuration similar to ansa-metallocene and showed good activity towards ethylene polymerization after activation with MAO.