A Macrocyclic 2,2′‐Bibenzimidazole Ruthenium(II) Chromophore as a Versatile Building Block for Supramolecular Devices

Abstract

We present the synthesis of a macrocyclic ruthenium(II) complex that combines the versatile photophysics and supramolecular chemistry of biimidazole ruthenium(II) chromophores with a macrocyclic geometry that allows for its introduction into mechanically interlocked frameworks. Struc- [a]4244 tural information on the core framework was gained from a solid-state structure. The new supramolecular building block shows that the principal photophysics of the ruthenium chromophore, that is, the cation-driven light-switch effect, are retained during the formation of the macrocycle.

Protonation‐Dependent Luminescence of an Iridium(III) Bibenzimidazole Chromophore

“…[10,38,[46][47][48] The doubly protonated complex Ir(tmBBI)-H 2 shows a structured emission band with two clear maxima (λ = 521 and 559 nm) and one shoulder at λ ≈ 612 nm, which can be completely regenerated from the deprotonated forms Ir(tmBBI)-H x (x = 0, 1) in solution upon the addition of aqueous HPF 6 , a procedure that has been successful with structurally related ruthenium complexes. [8] Upon single deprotonation, the emission is shifted hypsochromically with a slight decrease of the luminescence intensity. Again, the emission consists of two maxima (λ = 508 and 548 nm, the right is one flattened) and one shoulder at λ = 589 nm.…”

“…In their fully deprotonated state, these complexes act as metalloligands, that is, the deprotonated biimidazole sphere can bind a second metal center such as zinc(II), nickel(II), or copper(I). [1,2,8,9] The binding of these metal centers results in significant changes to their photophysical properties. This feature, which can be observed for various kinds of bi-(benz)imidazole metal complexes, is of paramount importance for this and further studies, as it can provide a spectroscopic tool for the direct observation of proton release from these molecules.…”

Ruthenium Imidazophenanthrolinium Complexes with Prolonged Excited‐State Lifetimes

“…[24] For detailed mechanistic investigations of the underlying principles of light-induced catalysis, photochemical molecular devices (PMDs) consisting of a photocenter, a bridging ligand, and a coordinated catalytic center have great potential. [25] We recently reported the synthesis of the new ruthenium complex [(tbbpy) 2 Ru(bbip)][PF 6 ] 3 {1; tbbpy = 4,4Ј-di-tertbutyl-2,2Ј-bipyridine, bbip = 1,3-(bisbenzyl)-1H-imidazo [4,5-f] [1,10]phenanthrolinium; Figure 1}, which already satisfies requirements (1)- (4). [26] This chromophore contains the potential bridging ligand bbip, which combines a phenanthroline moiety for coordination to the ruthenium center as well as an imidazolium part as a protonated Nheterocyclic carbene (NHC) precursor for the coordination of low-valent metal catalysts on the other side.…”

“…Ruthenium polypyridyl complexes are versatile molecular scaffolds for various applications, such as photodynamic therapy, [1][2][3][4][5][6] supramolecular machines and devices, [7][8][9][10] and luminescent sensors and switches. [11][12][13][14] Owing to their remarkably stable photoredox chemistry, many ruthenium polypyridyl complexes are potent chromophores for lightdriven catalysis, [15,16] dye-sensitized solar cells, [17][18][19] and photocatalytic water splitting.…”

Interaction of an Iridium(III)–Bibenzimidazole Complex with Anions – Implications for Luminescent Sensing

“…[1,3,[6][7][8][9][10][11][12][13][14][15][16][17][18] Regarding these observations, many workgroups have used Ru IIpolypyridyl complexes as chromophores, in which functional groups such as amide, pyrrole, pyrimidine, thiourea, urea, and imidazole ligands, [2,[19][20][21] but also other H-bond-donor functionalities, are appended and form hydrogen bonds with anions. [2,[19][20][21][29][30][31]38,39] The three different protonation states of these ligands (biimH x , x = 0, 1, 2) are controlled by several factors: (1) the acidity of the metalloreceptor, (2) the basicity of the distinct anions, and (3) the strength and steric demand of the hydrogen bonding, which should be related to the charge and interaction between the hydrogen-bond-donor and -acceptor groups. The most significant feature of such compositions is that the biimH 2 ligand has a classic bifunctionality: the imino moieties can be coordinated to transition metal fragments in a chelating mode, and the amino groups are proved to form twofold hydrogen bonds with various anions, initially as second-sphere coordination.…”