Generation of multimillion chemical space based on the parallel Groebke-Blackburn-Bienaymé reaction.

Parallel Groebke-Blackburn-Bienaymé reaction was evaluated as a source of multimillion chemically accessible chemical space. Two most popular classical protocols involving the use of Sc(OTf)3 and TsOH as the catalysts were tested on a broad substrate scope, and prevalence of the first method was clearly demonstrated. Furthermore, the scope and limitations of the procedure were established. A model 790-member library was obtained with 85% synthesis success rate. These results were used to generate a 271-Mln. readily accessible (REAL) heterocyclic chemical space mostly containing unique chemotypes, which was confirmed by comparative analysis with commercially available compound collections. Meanwhile, this chemical space contained 432 compounds that already showed biological activity according to the ChEMBL database.

Spectroscopic and Theoretical Insights into Surprisingly Effective Sm(III) Extraction from Alkaline Aqueous Media by o-Phenylenediamine-Derived Sulfonamides.

Alkaline high-level waste (HLW) generated as a result of years of nuclear weapons production has complicated composition and requires comprehensive treatment methods, which would allow concentrating its most radiotoxic components in a small volume for geological disposal. We have investigated six alkyl-substituted o-phenylenediamine-derived sulfonamides for extraction and consecutive stripping of Sm(III) from alkaline aqueous media. Up to 81% of Sm(III) recovery at pH 13.0-13.5 was achieved by disulfonamide (dsa) or dsa/Et3N in CH2Cl2, measured after contact with organic phases and subsequent stripping with 0.1 M HNO3. The use of Et3N dramatically enhances Sm(III) extraction at lower pH ranges (10.5-11.5) but decreases extraction at pH 13.0-13.5, while control experiments with Et3N and no dsa showed no extraction. Analysis of the extraction equilibria gave a 1:1 sulfonamide-Sm(III) complexation ratio, with the extracted species also presumed to contain coordinated H2O or OH-, as also shown by DFT calculations. Titration experiments of sulfonamides with Sm(III) in CH3CN were consistent with a 1:1 complexation ratio of dsa-6 to Sm(III) with a K11 = 6.6 × 107 M-1 derived from nonlinear regression analysis of the 1:1 binding isotherm. Theoretical DFT calculations determined the structures of possible species formed during extraction and the thermodynamics of extraction processes based on several initial [Sm(OH)y(NO3)z(H2O)x]3-y-z species and 1:1 Sm(III)/dsa-32- complexes formed in the organic phase, in which dsa complexes to Sm(III) in its bis-deprotonated form (denoted below as dsa-32-). Organization of close ion pairs of type {Na[Sm(dsa-32-)(OH)2]·2H2O} was shown to be thermodynamically favorable for extraction from alkaline aqueous media with pH = 13.0-13.5. Theoretical calculations also demonstrated thermodynamically favorable coordination to Am(III).

Coordination polymers of CdII and PbII with croconate show remarkable differences in coordination patterns: a structural and spectroscopic study.

The croconate dianion is a highly versatile ligand with two tautomeric forms making it useful for building large superstructures in the solid state. The single-crystal X-ray structures of PbII- and CdII-croconate coordination polymers, namely catena-poly[[[diaqualead(II)]-µ-croconato-κ4O1,O2:O3,O4] monohydrate], {[Pb(C5O5)(H2O)2]·H2O}n, 1, and catena-poly[[triaquacadmium(II)]-µ-croconato-κ4O1,O2:O3,O4], [Cd(C5O5)(H2O)3]n, 2, have been determined. Both polymers form one-dimensional (1D) structures; 1 is a nonplanar 1D zigzag coordination polymer extended along the crystallographic b axis, whereas 2 is a planar 1D ribbon parallel to the [101] direction. In 2, three H2O molecules are coordinated directly to the metal atom, while in 1, only two H2O molecules are directly coordinated to the metal atom. A third interstitial H2O molecule is involved in hydrogen bonding with O atoms of the croconate ligands of an adjacent layer and other H2O molecules, resulting in stacked double layers parallel to the [105] plane. Solid-state FT-IR and solution UV-Vis spectra also substantiate the croconate coordination.

A Redox-Induced Spin-State Cascade in a Mixed-Valent Fe3 (µ3 -O) Triangle.

One-electron reduction of a pyrazolate-bridged triangular Fe3 (µ3 -O) core induces a cascade wherein all three metal centers switch from high-spin Fe3+ to low-spin Fe2.66+ . This hypothesis is supported by spectroscopic data (1 H-NMR, UV-vis-NIR, infra-red, 57 Fe-Mössbauer, EPR), X-ray crystallographic characterization of the cluster in both oxidation states and also density functional theory. The reduction induces substantial contraction in all bond lengths around the metal centers, along with diagnostic shifts in the spectroscopic parameters. This is, to the best of our knowledge, the first example of a one-electron redox event causing concerted change in multiple iron centers.

Double exchange in a mixed-valent octanuclear iron cluster, [Fe8(µ4-O)4(µ-4-Cl-pz)12Cl4](-).

A combination of SQUID and pulsed high-field magnetometry is used to probe the nature of mixed valency in an Fe(II)Fe7(III) cluster. DFT-computed spin Hamiltonian parameters suggest that antiferromagnetic coupling dominates, and that electron transfer both between the four irons of the cubane core (t1) and between a cubane and three neighboring irons (t2) is significant. Simulations using the computed parameters are able to reproduce the key features of the measured effective magnetic moment, µeff(T), over the 2 < T < 300 K temperature range. In contrast, the field dependence of the molar magnetization, Mmol, measured at 0.4 K is inconsistent with substantial electron transfer: only values of t2∼ 0 place the separation between ground and first excited states in the region indicated by experiment. The apparent quenching of the cubane-outer electron transfer at very low temperatures indicates that vibronic coupling generates one or more shallow minima on the adiabatic potential energy surfaces that serve to trap the itinerant electron in the cubane core.

Self-assembly hexanuclear metallacontainer hosting halogenated guest species and sustaining structure of 3D coordination framework.

Chloride-centered hexanuclear hydroxopyrazolate reveals potential as a receptor of halomethane and halometallate species and as a molecular building block for coordination polymers.

Zinc(II) and cadmium(II) chloride complexes with 4,4'-bi-1,2,4-triazole.

New coordination compounds with the 4,4'-bi-1,2,4-triazole ligand (btr), namely tetraaqua-2kappa(4)O-di-mu(2)-4,4'-bi-1,2,4-triazole-1:2kappa(2)N(1):N(1');2:3kappa(2)N(1):N(1')-hexachlorido-1kappa(3)Cl,3kappa(3)Cl-trizinc(II), [Zn(3)Cl(6)(C(4)H(4)N(6))(2)(H(2)O)(4)], (I), and poly[cadmium(II)-mu(2)-4,4'-bi-1,2,4-triazole-kappa(2)N(1):N(2)-di-mu(2)-chlorido], [CdCl(2)(C(4)H(4)N(6))](n), (II), reveal an unprecedented molecular zwitterionic structure for (I) and a polymeric two-dimensional layer structure for (II). Differences between these products, which involve the formation of either charge-separated chlorometallate/aquametal fragments or complementary organic and inorganic bridges, are attributable to the hardness-softness characters of the metal cations. In (I), two N(1),N(1')-bidentate btr molecules connect one [Zn(H(2)O)(4)](2+) cation and two [ZnCl(3)](-) anions into a linear trizinc motif (the Zn atom of the cation occupies a centre of inversion in an N(2)O(4) coordination octahedron, whereas the Zn atom of the anion possesses a distorted tetrahedral Cl(3)N environment). In (II), the distorted vertex-sharing CdCl(4)N(2) octahedra are linked into binuclear [Cd(2)(mu(2)-Cl)(mu(2)-btr)(2)](3+) fragments by unprecedented N(1):N(2)-bidentate btr double bridges and bridging chloride ligands, while the additional chloride anions are also bridging, providing further propagation of the fragments into a two-dimensional network [Cd-Cl = 2.5869 (2)-2.6248 (7) A].

Metal-organic frameworks incorporating Cu3(mu3-OH) clusters.

Interaction of 4,4-bi(1,2,4-triazole) (btr) with copper(II) chloride (bromide) in aqueous or aqueous alcohol media led to a series of coordination polymers featuring the formation of mu 3-hydroxotricopper(II) clusters and their integration into 3D frameworks. These unprecedented structures originate in the propagation of trigonal hydroxotricopper(II) clusters bridged by tri- or tetradentate organic ligands. Complex [{Cu3(mu3-OH)}{Cu3(mu3-O)}(mu4-btr)3(H2O)4(OH)2Cl6]Cl.0.5H2O adopts a structure of SrSi2 topology, with eight-fold interpenetration of the coordination frameworks. The structure of [{Cu3(mu3-OH)}2(mu3-btr)6(mu4-btr)(mu-X)X4]X5.nH2O (X = Br, n = 6; X = Cl, n = 8) involves 2D coordination layers [{Cu3(mu3-OH)}(mu3-btr)3]n with an exceptional (3,6)-net topology, which are cross-linked by tetradentate btr ligands and bridging chloride (bromide) ions.