Erman Karakuş

Palladium-catalyzed alkoxycarbonylation of (Z)-2-en-4-yn carbonates leading to 2,3,5-trienoates.

Pd(0)-catalyzed carbonylation of (Z)-2-en-4-yn carbonates in the presence of a balloon pressure of CO in an alcohol donates vinylallenyl esters with an exclusively E-configuration and in high yields. The fact that no such reactivity could be observed with E-configured enyne carbonates may indicate that the reaction is promoted via the cooperative coordination of palladium with both alkynyl and carbonate moieties.

A Ratiometric Fluorescent Probe for Gold and Mercury Ions

A fluorescent probe that displays a ratiometric fluorescence response towards gold and mercury ions has been devised. Emitting at a relatively longer wavelength, the conjugated form of the fluorescent dye transforms in the presence of the gold or mercury ions into a new dye, the molecular structure of which lacks the conjugation and consequently emits at a distinctly shorter wavelength.

A BODIPY-based fluorescent probe for ratiometric detection of gold ions: utilization of Z-enynol as the reactive unit.

Using an irreversible intramolecular cyclisation pathway triggered by gold ions, a boron-dipyrromethene (BODIPY) based fluorescent probe integrated with a reactive Z-enynol motif responds selectively to gold ions. With the addition of gold(iii), the probe displays ratiometric fluorescence behaviour clearly observable to the naked eye under both visible and UV light.

Rhodium- and palladium-catalyzed 1,5-substitution reactions of 2-en-4-yne acetates and carbonates with organoboronic acids.

Two methods involving the rhodium-catalyzed reaction of 2-en-4-yne acetates and the palladium-catalyzed reaction of 2-en-4-yne carbonates with organoboronic acids were investigated; both afforded exclusively the (E)-configured vinylallenes. The coordinative interaction of the rhodium with the acetate group promoted the δ-elimination of Rh(I)-OAc from the alkenylrhodium intermediate II in both syn and anti modes, with the syn-elimination being the major path. DFT calculations revealed that a conformer of this intermediate (II), which can lead to the (E)-configured vinylallene product via the syn-elimination mode, is energetically the most favorable conformer. The rhodium-catalyzed procedure is not applicable to reactions involving (E)-configured enyne acetates, because the geometry of the alkenylrhodium intermediate that is derived from the corresponding (E)-enyne acetate would not allow such coordinative interaction to occur. The palladium-catalyzed method, which proceeds through formation of the σ-vinylallenylpalladium intermediate, B, is suitable for both the (E)- and (Z)-configured enyne carbonates and appears to have a wider scope for both organoboronic acids and enyne substrates. The palladium-catalyzed reaction of an enantiomerically enriched enyne carbonate proceeded with racemization.

BODIPY–Au(I): A Photosensitizer for Singlet Oxygen Generation and Photodynamic Therapy

Upon complexation with Au(I), a photoinactive BODIPY derivative was transformed into a highly photoactive triplet sensitizer. Along with high efficiency in singlet oxygen generation (ΦΔ = 0.84), the new BODIPY-Au(I) skeleton showed excellent photocytotoxic activity against cancer cell lines (EC50 = 2.5 nM).

A BODIPY/pyridine conjugate for reversible fluorescence detection of gold(III) ions

We designed a “turn-on” type fluorescent probe based on a BODIPY–pyridine conjugate which exhibits high selectivity towards Au(III) ions and, also responds to changes in the pH within the acidic pH range. The probe offers features such as a rapid response time, a low detection limit, and high sensitivity and selectivity. The detection of Au(III) is recognized by a distinct change in the emission intensity which relies on a reversible “ligand to ion” binding mechanism. We also document the utility of the probe for the quantification of gold ion residues in synthetic end products prepared via gold catalysis.

A guanidinium modified rhodamine-based fluorescent probe for in vitro/vivo imaging of gold ions

We devised a rhodamine-based fluorescent probe functionalized with a guanidinium moiety, which both operates efficiently in pure aqueous media and displays a selective fluorescence response to Au3+ ions. We also demonstrated the successful fluorescence imaging of Au3+ within living cells and a vertebrate species, the zebrafish.

A BODIPY‐Based Fluorescent Probe to Visually Detect Phosgene: Toward the Development of a Handheld Phosgene Detector

A boron-dipyrromethene (BODIPY)-based fluorescent probe with a phosgene-specific reactive motif shows remarkable selectivity toward phosgene, in the presence of which the nonfluorescent dye rapidly transforms into a new structure and induces a fluorescent response clearly observable to the naked eye under ultraviolet light. Given that dynamic, a prototypical handheld phosgene detector with a promising sensing capability that expedites the detection of gaseous phosgene without sophisticated instrumentation was developed. The proposed method using the handheld detector involves a rapid response period suitable for issuing early warnings during emergency situations.