The structural features required for mitochondrial uptake of BODIPY-based optical imaging agents have been explored. The first derivatives of this class of dyes shown to have mitochondrial membrane potential-dependent uptake in both cancer and heart cells have been developed.
The properties of 13 monodentate P-donor ligands not previously characterized in the Ligand Knowledge Base (LKB) approach have been determined computationally, allowing NEW LIGANDS ON LKB-P PROPERTY MAP 707 their addition to the LKB-P map of ligand space. 1 Consideration of ligand positions and close neighbors in ligand space can help to establish a chemical context and hence guide their application to organometallic catalysis. Here we demonstrate this potential application of the LKB-P map and discuss known and likely applications of these ligands.
Here we report a study on the reactivity of the fluorescent air-stable primary phosphine 8-((4-phosphino)phenyl)-4,4-dimethyl-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene 4 with [Mo (CO) 6 ], [W(CO) 6 ], [Mo(CO) 4 (piperidine)] and [W(CO) 4 (piperidine)] which yields the mono-phosphine [Mo(CO) 5 (4)] 5, [W(CO) 5 (4)] 6 and di-phosphine cis-[Mo(CO) 4 (4) 2 ] (7) and cis-[W(CO) 4 (4) 2 ] (9) complexes as the predominant products. In addition to the characterisation of these complexes by multinuclear NMR and IR spectroscopy, and mass spectrometry, the solid state structures of 6 and cis-7 have also been determined by single crystal X-ray diffraction. The photophysical properties of the complexes show that the incorporation of the phosphorus ligand has a limited effect on the absorption and emission profile of the Bodipy core and that they retain similar quantum yields to their parent Bodipy dyes. Small quantities of the by-products trans-[Mo(CO) 4 (4) 2 ] (7), cis-[Mo(CO) 4 (piperidine)(4)] (8) and cis-[W(CO) 4 (piperidine)(4)] (10) were also isolated and characterized.
Air-stable, fluorescent primary phosphines have been prepared on a multigram scale. The two key synthetic steps are an optimized palladium-catalyzed phosphonylation of aryl bromides and a boron-carbon bond formation reaction. The method provides a valuable synthetic route to novel fluorescent derivatives via a key phosphonate intermediate.Primary phosphines are largely regarded as troublesome compounds from the perspective of synthetic methodology, due to their reputation as highly air-sensitive, volatile, toxic, and pyrophoric compounds. 1 The low air stability of many primary phosphines has made them an under-utilized class of ligand; however, they are versatile starting materials due to functionalization of the phosphorus-hydrogen bonds. In recent years, a very limited number of 'user-friendly' primary phosphines have been reported, 2 some of which take advantage of steric encumbrance in order to afford kinetic stability towards air oxidation. 3 A handful of other primary phosphines whose unexplained and surprising air stability cannot be accounted for on steric grounds have also appeared in the literature. 4 Very recently, we discovered the first air-stable fluorescent primary phosphines 1a and 1b based on Bodipy ( Figure 1). 5 According to our density functional theory-based model, their air stability is attributable to the high level of π-conjugation in the Bodipy backbone. 5, 6 We have also shown that despite this resistance to air oxidation (in air, no oxidation in the solid state or in chloroform solution after seven days was observed 5,6 ), the phosphino group remains readily transformable to yield fluorescent derivatives of, for example, Triphos ( Figure 1). 5 Tridentate phosphine 2 has been shown by us to form stable chelates with rhenium, 5 a metal used as a nonradioactive substitute for the gamma emitter 99m Tc. Such complexes have potential as dual imaging agents by combining the desirable photophysical properties of the Bodipy fluorophore 7 for in vitro fluorescence microscopy, together with the in vivo radioimaging afforded by virtue of the 99m Tc center. 5 Figure 1Bodipy primary phosphines 1a and 1b and the tridentate phosphine 2, which is a fluorescent analogue of TriphosThe potential of 1a and 1b as ligand precursors is thus clear and we therefore sought an efficient large-scale synthesis of them. The aforementioned synthetic approach was reevaluated and two problematic steps were identified as (i) the substitution of the Bodipy fluorides for alkyl or aryl groups, as the dyes are formed in low yields (Scheme 1, step ii 44%: 4a, 40%: 4b) and (ii) the carbonphosphorus coupling reaction, affording the diethyl phosphonates, is hindered by a reaction time of three days and a yield of 53% for 5b (Scheme 1, step iii). These factors limited the previous syntheses to a scale of less than one gram. 5Herein we report a significantly improved synthetic method for preparing the primary phosphines 1a and 1b in multigram quantities via a simplified and improved approach, with the focus on the phosphonylatio...
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