Photochromic Dithienylethene- Phenanthroline Ligands and their Corresponding Ru(II) Complexes

Abstract

Dithienylethene-phenanthroline ligands as new photochromic systems are described. The photochemical and photophysical properties are strongly influenced by the substituents on the thiophene moiety. The photochromic properties are lost, if one or two methyl groups in position 2 and/or 2' of the target molecules (2o, 3o, 4o) are replaced by isopropyl groups. Replacement of a methyl group by a phenyl group in position 5 and/or 5' shifts the absorption maxima from 514 nm to 575 nm for the free ligand (1c, 2c) and from 530 nm to 613 nm for the corresponding ruthenium complex (Ru(1c), Ru(2c)) in its closed form. Unfortunately, the photochromic unit in its closed form can be reopened by a back reaction in the dark at room temperature. Complex Ru(2o) shows an emission with a maximum at 608 nm. The emission is quenched if the metal complex is in its closed form (Ru(2c)). Fatigue resistance is better for complex Ru(2o) than for the free ligand (2o).

Stille Expands the Family: Access to 5,6‐Bis‐2‐thienyl‐Substituted Phenanthroline Under Mild Conditions for Luminescent Ruthenium Complexes

“…These results are in line with previously reported absorption properties of 5,6‐bis‐thiophene‐phenanthrolines, accessible via Suzuki‐coupling reactions (L1–4) which have been performed in benzene and acetonitrile, respectively (Table and Scheme ), , ,…”

A multi‐addressable molecular switch based on a novel diarylethene with an imidazo [4,5‐f] [1,10] phenanthroline unit

“…Phenanthroline is an intriguing compound as fluorescence ligand because its nitrogen atoms in 1 and 10 positions can coordinate with transition metals. Yam and coworkers developed a series of photochromic 5,6‐dithienyl‐1,10‐phenanthroline ligands, which could be coordinated with different metal centers to tune the photochromism with a wide variety of different metal complexes . In addition, the phenanthroline can be modified to form imidazo [4,5‐ f ] [1,10] phenanthroline compounds, in which the NH group in imidazole ring is able to act as fluorimetric sensor for anions .…”

“…Yam and coworkers developed a series of photochromic 5,6-dithienyl-1,10-phenanthroline ligands, [37] which could be coordinated with different metal centers to tune the photochromism with a wide variety of different metal complexes. [38][39][40][41] In addition, the phenanthroline can be modified to form imidazo [4,5-f] [1,10] phenanthroline compounds, in which the NH group in imidazole ring is able to act as fluorimetric sensor for anions. [42] For instance, Wang et al reported a Eu(III) complex containing imidazo [4,5-f] [1,10] phenanthroline, in which the addition of F -, HSO 4 -, and AcOcaused significant changes in the absorption and emission spectra.…”

Optoelectronic Properties and Holographic Optical Recording of a Unsymmetrical Diarylethene Having a Pyrrole Unit

“…In general, the molecule undergoes a photocyclization reaction if it is orientated in an anti-parallel array and if the distance between two reactive carbon atoms on the aryl moiety is within 0.42 nm [10]. The photochromic reactivity depends on several factors, such as conformation of the open-ring isomer, the categories of heteroaryl moieties, electron donor/acceptor substituents, and conjugation length of the heteroaryl groups [11][12][13][14][15]. Particularly, the categories of heteroaryl moieties and substituents on the reactive position greatly influence the photoreactivity.…”