Crystal structure of chalcogenides R'xR''yR'''zPbSi2S8 (R' – La, R'' – Tb, R''' – Er)

The chalcogenides LaxTbyErzPbSi2S8 were obtained by synthesizing the elementary components in vacuum quartz containers at 1320 K. The synthesized alloys were homogenized by annealing at 770 K during 500 hours. The cell parameters of synthesized sulfides are: a = 0,89576(3) nm, c = 2,65646(8) nm – La1,2Tb0,4Er0,4PbSi2S8; a = 0,89209(1) nm, c = 2,63466(5) nm – La0,9Tb0,2Er0,9PbSi2S8; a = 0,89002(3) nm, c = 2,62714(7) nm – La0,67Tb0,67Er0,67PbSi2S8; a = 0,88993(1) nm, c = 2,62973(4) nm – La0,6Tb1,2Er0,2PbSi2S8; a = 0,885161(7) nm, c = 2,60445(3) nm – La0,2Tb0,9Er0,9PbSi2S8 respectively. The atoms of statistical mixture (La,Tb,Er,Pb) occupy the site 18e (x y 1/4), and the atoms of Si occupy the site 12c (1/3 2/3 z) in the structure of the obtained chalcogenides. Coordinating polyhedra of atoms of the statistical mixture (La, Tb, Er, Pb) are trigonal prism with two additional atoms (CN = 8), and the atoms of Si occupying the crystallographic point system 12c describes with the tetrahedron. According to the results of the experiment, the synthesized chalcogenides crystallize in the structure type of La2PbSi2S8 (hR26,167). The structure of La2PbSi2S8 is described by using the theory of second anion coordination (SAC).

The Synthesis of Biarylmonophosphonates via Palladium-Catalyzed Phosphonation, Iridium-Catalyzed C-H Borylation, Palladium-Catalyzed Suzuki–Miyaura Cross-Coupling

The iridium-catalyzed C-H borylation of diethyl phenylphosphonate results in nonselective mono and bisborylation to afford a near statistical mixture of 3-, 3,5- and 4-boryl substituted aryl phosphonates whereas 3-substituted aryl phosphonates undergo highly regioselective C-H borylation to afford the corresponding meta-phosphonate substituted arylboronic esters as the sole product; the resulting boronic esters were used as nucleophilic reagents in a subsequent palladium-catalyzed Suzuki–Miyaura cross-coupling to generate a range of biarylmonophosphonates. Gratifyingly, the Suzuki–Miyaura cross-coupling can be conducted without purifying the boronic ester which greatly simplifies the synthetic procedure. Graphical Abstract

Multifunctional streptavidin–biotin conjugates with precise stoichiometries

Multifunctional streptavidin-biotin conjugates with defined stoichiometry and number of open binding pockets provide molecularly precise alternatives to the statistical mixture of products that typically forms.

Remarkable self-sorting selectivity in covalently linked homochiral and heterochiral pairs driven by Pd2L4 helicate formation

Remarkable self-sorting selectivity is demonstrated between LRR and LRS through a Pd2L4 assembly. By contrast, mixing of LRR and LSS with Pd2+ produces a near statistical mixture.