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1. A Comparison of the Photophysical, Electrochemical and Cytotoxic Properties of meso-(2-, 3- and 4-Pyridyl)-BODIPYs and Their Derivatives

   https://doi.org/10.3390/s22145121  

   Ndung’u, Caroline; LaMaster, Daniel J.; Dhingra, Simran; Mitchell, Nathan H.; Bobadova-Parvanova, Petia; Fronczek, Frank R.; Elgrishi, Noémie; Vicente, Maria da (July 2022, Sensors)

   Boron dipyrromethene (BODIPY) dyes bearing a pyridyl moiety have been used as metal ion sensors, pH sensors, fluorescence probes, and as sensitizers for phototherapy. A comparative study of the properties of the three structural isomers of meso-pyridyl-BODIPYs, their 2,6-dichloro derivatives, and their corresponding methylated cationic pyridinium-BODIPYs was conducted using spectroscopic and electrochemical methods, X-ray analyses, and TD-DFT calculations. Among the neutral derivatives, the 3Py and 4Py isomers showed the highest relative fluorescence quantum yields in organic solvents, which were further enhanced 2-4-fold via the introduction of two chlorines at the 2,6-positions. Among the cationic derivatives, the 2catPy showed the highest relative fluorescence quantum yield in organic solvents, which was further enhanced by the use of a bulky counter anion (PF6−). In water, the quantum yields were greatly reduced for all three isomers but were shown to be enhanced upon introduction of 2,6-dichloro groups. Our results indicate that 2,6-dichloro-meso-(2- and 3-pyridinium)-BODIPYs are the most promising for sensing applications. Furthermore, all pyridinium BODIPYs are highly water-soluble and display low cytotoxicity towards human HEp2 cells. 

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2. 8(meso)-Pyridyl-BODIPYs: Effects of 2,6-Substitution with Electron-Withdrawing Nitro, Chloro, and Methoxycarbonyl Groups

   https://doi.org/10.3390/molecules28124581  

   Ndung’U, Caroline; Bobadova-Parvanova, Petia; LaMaster, Daniel J.; Goliber, Dylan; Fronczek, Frank R.; Vicente, Maria da (June 2023, Molecules)

   The introduction of electron-withdrawing groups on 8(meso)-pyridyl-BODIPYs tends to increase the fluorescence quantum yields of this type of compound due to the decrease in electronic charge density on the BODIPY core. A new series of 8(meso)-pyridyl-BODIPYs bearing a 2-, 3-, or 4-pyridyl group was synthesized and functionalized with nitro and chlorine groups at the 2,6-positions. The 2,6-methoxycarbonyl-8-pyridyl-BODIPYs analogs were also synthesized by condensation of 2,4-dimethyl-3-methoxycarbonyl-pyrrole with 2-, 3-, or 4-formylpyridine followed by oxidation and boron complexation. The structures and spectroscopic properties of the new series of 8(meso)-pyridyl-BODIPYs were investigated both experimentally and computationally. The BODIPYs bearing 2,6-methoxycarbonyl groups showed enhanced relative fluorescence quantum yields in polar organic solvents due to their electron-withdrawing effect. However, the introduction of a single nitro group significantly quenched the fluorescence of the BODIPYs and caused hypsochromic shifts in the absorption and emission bands. The introduction of a chloro substituent partially restored the fluorescence of the mono-nitro-BODIPYs and induced significant bathochromic shifts. 

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3. Manganese catalysed dehydrocoupling of silanes and siloxanes with ammonia to prepare oligosilazanes and polysiloxazanes

   https://doi.org/10.1039/d4dt01982b  

   Mehta, Gautam K; Nguyen, Thao T; Flores, Marco; Trovitch, Ryan J (August 2024, Dalton Transactions)

   The halogen-free synthesis of oligosilazanes has been observed upon dehydrocoupling silanes with ammonia at 25 °C using [(2,6-iPr2PhBDI)Mn(µ-H)]2. Extending this methodology to polymethyl-hydrosiloxanes afforded thermally robust polysiloxazane solids, and the dehydrocoupling of 1,3,5,7-tetramethylcyclotetrasiloxane with ammonia afforded a polysiloxazane having a weight-average molecular weight of 4300 g/mol. A representative oligosilazane has been applied to a copper surface and found to afford a 20 μm thick coating that resists corrosion after 24 h under water. Addition of ammonia to [(2,6-iPr2PhBDI)Mn(µ-H)]2 allowed for characterization of the catalyst resting state, [(2,6-iPr2PhBDI)Mn(µ-NH2)]2, which has been found to mediate Si‒N dehydrocoupling. 

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4. POCOP-type cobalt and nickel pincer complexes bearing an appended phosphinite group

   https://doi.org/10.1139/cjc-2020-0137  

   Li, Yingze; Krause, Jeanette A.; Guan, Hairong (April 2021, Canadian Journal of Chemistry)

   The reaction of 1,3,5-( i Pr 2 PO) 3 C 6 H 3 with Co 2 (CO) 8 leads to the isolation of a POCOP-type mononuclear pincer complex {κ P ,κ C ,κ P -2,4,6-( i Pr 2 PO) 3 C 6 H 2 }Co(CO) 2 (1) or a tetranuclear species {κ P -{κ P ,κ C ,κ P -2,4,6-( i Pr 2 PO) 3 C 6 H 2 }Co(CO) 2 } 2 Co 2 (CO) 6 (2), depending on the ligand to cobalt ratio employed. The latter compound can be an impurity during the synthesis of {2,6-( i Pr 2 PO) 2 -4-Me 2 N-C 6 H 2 }Co(CO) 2 , when the ligand precursor 5-(dimethylamino)resorcinol is contaminated with phloroglucinol due to incomplete monoamination. Similarly, the reaction of 1,3,5-( i Pr 2 PO) 3 C 6 H 3 with NiCl 2 in the presence of 4-dimethylaminopyridine provides {κ P ,κ C ,κ P -2,4,6-( i Pr 2 PO) 3 C 6 H 2 }NiCl (3) bearing an appended phosphinite group. Structures 1–3 have been studied by X-ray crystallography. 

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5. Synthesis of a light-harvesting ruthenium porphyrin complex substituted with BODIPY units. Implications for visible light-promoted catalytic oxidations

   https://doi.org/10.1039/D1NJ00189B  

   Malone, Jonathan; Klaine, Seth; Alcantar, Christian; Bratcher, Fox; Zhang, Rui (March 2021, New Journal of Chemistry)

   null (Ed.)

   A light-harvesting ruthenium porphyrin substituted covalently with four boron–dipyrrin (BODIPY) moieties has been synthesized and studied. The resulting complex showed an efficient decarbonylation reaction predominantly due to a photo-induced energy transfer process. Chemical oxidation of the ruthenium( ii ) BODIPY–porphyrin afforded a high-energy trans -dioxoruthenium( vi ) species that is one order of magnitude more reactive towards alkene oxidation than those analogues supported by conventional porphyrins. In the presence of visible light, the ruthenium( ii ) BODIPY–porphyrin displayed remarkable catalytic activity toward sulfide oxidation and alkene epoxidation using iodobenzene diacetate [PhI(OAc) 2 ] and 2,6-dichloropyridine N -oxide (Cl 2 pyNO) as terminal oxidants, respectively. The findings in this work highlight that porphyrin–BODIPY conjugated metal complexes are potentially useful for visible light-promoted catalytic oxidations. 

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