Coordination Programming of Photofunctional Molecules

Abstract

Our recent achievements relating to photofunctional molecules are addressed. Section 1 discloses a new concept of photoisomerization. Pyridylpyrimidine-copper complexes undergo a ring inversion that can be modulated by the redox state of the copper center. In combination with an intermolecular photoelectron transfer (PET) initiated by the metal-to-ligand charge transfer (MLCT) transition of the Cu(I) state, we realize photonic regulation of the ring inversion. Section 2 reports on the first examples of heteroleptic bis(dipyrrinato)zinc(II) complexes. Conventional homoleptic bis(dipyrrinato)zinc(II) complexes suffered from low fluorescence quantum yields, whereas the heteroleptic ones feature bright fluorescence even in polar solvents. Section 3 describes our new findings on Pechmann dye, which was first synthesized in 1882. New synthetic procedures for Pechmann dye using dimethyl bis(arylethynyl)fumarate as a starting material gives rise to its new structural isomer. We also demonstrate potentiality of a donor-acceptor-donor type of Pechmann dye in organic electronics.

Photochemical Redox Reactions of Copper(II)–Alanine Complexes in Aqueous Solutions

“…There has been growing interest in the photochemical reactions of copper complexes in the environment and in biochemistry. − Copper is a ubiquitous transition metal, which has two accessible oxidation states. In natural waters and wastewaters, Cu(II) is thought to be present primarily as complexes with biogenic or anthropogenic ligands, many of which contain carboxylato and amino functional groups. − Copper complexes can participate in a large number of photochemical redox reactions in sunlit surface waters.…”

Heteroleptic [Bis(oxazoline)](dipyrrinato)zinc(II) Complexes: Bright and Circularly Polarized Luminescence from an Originally Achiral Dipyrrinato Ligand

“…[1] Although the lightemitting properties of BODIPYs are well known, it has long been believed that metal complexes of this ligand structure are non-emissive.E fforts over the last decade to develop fluorescent dipyrrin metal complexes (for example,Z n II , [2] In III , [3] Ga III , [3] Sn II , [4] Sn IV , [5] and Al III [6] complexes) have met with limited success. [10] Note that heterolepticity has been reported to improve the optical properties of several metal complexes. [10] Note that heterolepticity has been reported to improve the optical properties of several metal complexes.…”

“…[10] Note that heterolepticity has been reported to improve the optical properties of several metal complexes. [10,12] Thev alidity of our strategy has been further verified by heteroleptic tris(dipyrrinato)indium(III) [13a] and (azadipyrrinato)(dipyrrinato)zinc(II) [13b] complexes that also show brighter luminescence than the corresponding homoleptic complexes.The limitation of this strategy is clear when attempting to gain bright fluorescence from asimple,non-p- expanded dipyrrinato ligand (for example,t he left-hand dipyrrinato ligand of 1 in Figure 1a). This electronic structure leads to the suppression of non-emissive symmetry-breaking charge separation.…”

“…[7] Thus,d ipyrrin metal complexes have been regarded as useful components for self-assembled supramolecular and coordination polymer architectures [8] rather than luminophores.A lthough heteroleptic bis and tris(dipyrrinato)metal complexes were synthesized previously, [9] we have recently found that heteroleptic bis(dipyrrinato)zinc(II) complex 1 (Figure 1a)e xhibits ahigh fluorescence quantum yield. [10] Note that heterolepticity has been reported to improve the optical properties of several metal complexes. [11] Theb right luminescence of 1 arises from appropriate engineering of the frontier orbitals of the dipyrrinato ligands.T he HOMO and LUMO of 1 are located exclusively on the right-hand dipyrrinato ligand (containing the arylacetylene functional groups) because of the narrowing of the HOMO-LUMO gap upon p expansion ( Figure 1a).…”

Luminescent Heteroleptic Tris(dipyrrinato)indium(III) Complexes

“…However, metal complexes of dipyrrins have remained relatively neglected because of their low emission efficiencies. We recently developed a heteroleptic bis(dipyrrinato)zinc(II) complex that showed a unprecedentedly high fluorescence quantum yield . Improvement was gained through suppression of the formation of nonemissive charge-separated states between the two dipyrrinato ligands that compete with the emissive 1 π–π* state (Figures S1–S3 in the Supporting Information, SI).…”