Light-driven Au(III)-promoted cleavage of triazole-bearing amine derivatives and its application in the detection of ionic gold.

Light-driven Au(III)-promoted oxidative cleavage of triazole-bearing amine derivatives is utilized for the detection of ionic gold in aqueous media. A bistriazole-bearing boron dipyrromethane (1(BODIPY)) exhibited selective and sensitive fluorescence enhancement by the addition of Au(3+) and subsequent UV irradiation.

A porphyrin-based molecular tweezer: guest-induced switching of forward and backward photoinduced energy transfer.

A bisindole-bridged-porphyrin tweezer (1), a pair of zinc porphyrins (PZn's) connected to bisindole bridge (BB) via the Cu(I)-mediated alkyne-azide click chemistry, exhibited unique switching in forward and backward photoinduced energy transfer by specific guest bindings. The addition of Cu(2+) caused a change in electronic absorption and fluorescence quenching of 1. MALDI-TOF-MS and FT-IR analyses indicated the formation of stable coordination complex between 1 and Cu(2+) (1-Cu(II)). Without Cu(2+) coordination, the excitation energy flows from BB to PZn's with significantly high energy transfer efficiency. In contrast, the direction of energy flow in 1 was completely reversed by the coordination of Cu(2+). The difference in fluorescence quantum yield between 1 and 1-Cu(II) indicates that more than 95% of excitation energy of PZn flows into Cu(II)-coordinated BB. The energy transfer efficiency was further controlled by bidentate ligand coordination onto 1-Cu(II). When pyrophosphate ion was added to 1-Cu(II), the recovery of fluorescence emission from PZn was observed. The quantum mechanical calculations indicated that the Cu(II)-coordinated BB has square planar geometry, which can be distorted to form octahedral geometry due to the coordination of bidentate ligands.

Absolute stereochemical determination of chiral carboxylates using an achiral molecular tweezer.

A new type of molecular tweezer (1) has been synthesized for the direct determination of the absolute configuration of chiral carboxylates without analyte derivatization. Upon the addition of diamine and anionic guests, 1 exhibited shifts in its absorption spectrum with clear isosbestic points. The continuous variation method indicated that both the diamine and anionic guests form 1:1 host-guest complexes with 1 with very high binding affinity. When Boc-L-Ala (BLA) as a form of tetrabutylammonium salt was added to 1, a weak negative CD signal was observed. This weak CD signal was dramatically changed to a strong positive CD couplet upon addition of achiral 1,12-diaminododecane. Such a positive CD couplet was observed for all of the tested L-amino acid derivatives, while the D-amino acid derivatives gave the opposite signals. As a result of these unique characteristics of 1, it can be utilized as a highly sensitive probe for the absolute stereochemical determination of chiral carboxylates.

Synthesis of stable monoporphyrinate lanthanide(III) complexes without ancillary ligands.

A new type of porphyrin ligand bearing four triazole groups at the ortho-positions of phenyl rings in tetraphenylporphyrin was synthesized for the formation of monoporphyrinate lanthanide complexes without ancillary ligands.

A diketopyrrolopyrrole-based colorimetric and fluorescent probe for cyanide detection.

Red means CN: A new type of diketopyrrolopyrrole-based chromophore has been synthesized as a colorimetric and fluorescent probe for the detection of cyanide using only two reaction steps. Through the addition of cyanide to the chromophore, the fluorescence emission and color were greatly changed in a highly sensitive and selective manner.

A zinc porphyrin-based molecular probe for the determination of contamination in commercial acetonitrile.

A zinc porphyrin-based receptor containing four triazole groups at the ortho-position of each phenyl group (1) was utilized as a useful probe for the determination of contaminants in acetonitrile (MeCN). Through the simple observation of the absorption spectrum of 1 in MeCN, the cyanide contamination concentration could be directly determined.

A boradiazaindacene-based turn-on fluorescent probe for cyanide detection in aqueous media.

Turn on events: A molecular probe consisting of a boradiazaindacene unit conjugated with a dicyano-vinyl group has been designed for the selective and sensitive detection of cyanide by strong fluorescence enhancement in aqueous media (see scheme).

Strong binding affinity of a zinc-porphyrin-based receptor for halides through the cooperative effects of quadruple C-H hydrogen bonds and axial ligation.

A new type of host compound (1), tetraphenyl zinc-porphyrin (ZnTPP) that contains four triazole groups at the ortho-position of each phenyl group, has been synthesized and characterized by using (1)H, (13)C NMR, and MALDI-TOF-MS analyses. The host-guest complex formation between 1 and halides was investigated by using (1)H NMR spectroscopy in [D(6)]DMSO. The triazole, benzyl, and phenylene proton signals were shifted upfield by the addition of halides in the form of tetrabutylammonium salts, which implies that the triazole protons in 1 are allocated very closely to the porphyrin ring and are directed toward the binding pocket over the porphyrin ring during the formation of hydrogen bonds. The UV/Vis absorption spectra showed that both the Soret and Q band absorptions of 1 underwent a strong redshift due to the addition of halides. Compound 1 exhibited surprisingly strong binding affinities for the halides, where the association constants for Cl(-), Br(-), and I(-) binding were estimated to be larger than 10(8), 1.79×10(7), and 1.84×10(5) M(-1), respectively. The UV/Vis absorption changes and the result of competitive titration using 4-tert-butylpyridine indicated that the cooperative effects of axial coordination and C-H···X hydrogen bond interactions resulted in the strong binding affinity of 1 to halides.

Highly sensitive and selective cyanide detection via Cu2+ complex ligand exchange.

A new type of fluorescent probe (1) with two triazole groups that are conjugated with a carbazole moiety was synthesized by a Cu(I)-catalyzed alkyne-azide click reaction for the selective and sensitive detection of cyanide via fluorescence enhancement by ligand exchange and metal ion removal.

An indolocarbazole-bridged macrocyclic porphyrin dimer having homotropic allosterism with inhibitory control.

A macrocyclic host, a pair of zinc porphyrins bridged by two anion-acceptable indolocarbazole moieties, has shown strong positive homotropic allosterism upon anionic guest bindings with an inhibitory control mechanism by DABCO addition.

Cyclodipeptide-bridged porphyrin dimer supramolecular assemblies.

A cyclodipeptide-bridged porphyrin dimer has formed fibrous and toroidal multi-porphyrin array systems by hydrogen bonding-mediated self-assembly.