Luminescent Complexes of the Trinuclear Silver(I) and Copper(I) Pyrazolates Supported with Bis(diphenylphosphino)methane.

The first example of trinuclear copper(I) and silver(I) pyrazolates adducts with a tertiary diphosphine (Ph2PCH2PPh2) retaining trimeric [MPz]3 core is reported. Despite rather strong M-P bonding, the complexes are able to undergo the dissociation of one M-P bond leading to the "merry-go-round" movement of P atoms over the M3 triangle. The copper complex displays emission from 1MLCT and 3MLCT states. The triplet and singlet states are separated by a relatively small energy gap (1080 cm-1) that triggers the thermally activated delayed fluorescence (TADF) behavior and leads to the worthy quantum yield of 41% at 298 K. The silver complex in the solid state and frozen solution shows dual emission originating from the 1IL and 3MLCT states that is dictated by the much higher energy difference between the emissive singlet and triplet as well as by the essentially different nature of these states.

Novel base-initiated cascade reactions of hemiindigos to produce dipolar γ-carbolines and indole-fused pentacycles.

Novel continuous-flow cascade reactions are developed for producing 1,4-diaryl-disubstituted dipolar γ-carbolines 2 that contain a carboxylate group and their two pentacyclic precursors 6, 7 from hemiindigos 1. The nucleophilic and pro-electrophilic chemistry described is new to the hemiindigos 1, and it led to the discovery of antimycobacterial scaffold characteristic of rimino-type pentacycles 6, 7 and potent drug clofazimine. The new scaffold like clofazimine appears to be useful in developing lead agents active against drug-resistant/dormant TB.

New enolate-carbodiimide rearrangement in the concise synthesis of 6-amino-2,3-dihydro-4-pyridinones from homoallylamines.

Three-step synthesis of 6-amino-2,3-dihydro-4-pyridinones from homoallylamines involving NBS-mediated cyclization of N-(3-butenyl)ureas to 6-(bromomethyl)-2-iminourethanes, dehydrohalogenation and a novel rearrangement as a key step has been developed. The scope and limitations of the method, as well as the mechanism of the rearrangement, supported by kinetic studies and the isolation of N-(1-adamantyl)carbodiimide, are discussed. The final products, imino-analogues of well known piperidine-2,4-diones, are promising building blocks in the synthesis of bio-/pharmacological compounds.

Base-mediated transformation of the agostic (π-allyl)-closo-rhodacarboranes into complexes with an open (1-5-η5)-pentadienyl ligand.

The reactions of agostic (CH3···Rh) complexes [3-{(1-3-η(3))-1,1,2-trimethylallyl}-1-R-2-R'-closo-3,1,2-RhC2B9H9] [1: R = R' = Me; 2: R,R' = µ-(ortho-xylylene); 3: R = Ph, R' = Me] in a cooled (+5 °C) toluene solution with the strong non-nucleophilic base N,N,N',N'-tetramethylnaphthalene-1,8-diamine (tmnd) formally involve a linear coupling of the π-allyl ligand of one molecule of the complex to the π-allyl ligand of the second molecule of the complex, ultimately forming the structurally novel mononuclear species [3-{(1-5-η(5))-2,3-dimethyl-5-(3-methylbuten-2-yl)pentadienyl}-1-R-2-R'-closo-3,1,2-RhC2B9H9] (4, 5) and (6a,b, a mixture of diastereomers). Complexes 5 and 6a,b were also prepared using weaker bases such as PPh3 or even EtOH instead of tmnd. All new complexes 4-6 were characterized by a combination of analytical and multinuclear NMR data, as well as by single-crystal X-ray diffraction studies of two selected species 5 and the major diastereomer of 6, which revealed an open η(5)-pentadienyl coordination mode of the hydrocarbon ligands in these complexes.