Supramolecular coordination compounds bear exceptional advantages over their organic counterparts. They are available in one‐pot reactions and in high yields and display physical properties that are ...generally inaccessible with organic species. Moreover, their weak, reversible, noncovalent bonding interactions facilitate error checking and self‐correction. This Review emphasizes the achievements in supramolecular coordination chemistry initiated by serendipity and their materialization based on rational design. The recognition of similarities in the synthesis of different supramolecular assemblies allows prediction of potential results in related cases. Supramolecular synthesis obeys guidelines comparable to the “lead sheet” used by small jazz ensembles for improvisation and therefore more often leads to unpredicted results. The combination of detailed symmetry considerations with the basic rules of coordination chemistry has only recently allowed for the design of rational strategies for the construction of a variety of nanosized systems with specified size and shape.
Luck or ability? In the field of supramolecular coordination chemistry, impressive advances have been achieved by the augmentation of initial serendipitous discoveries with rational design. Detailed consideration of symmetry and of the basic principles of coordination chemistry have led to rational strategies for the construction of diverse nanostructures with specific form and size (for example, 1; Fe: white, tripodal benzene ligand: yellow).
The reaction of the cobalt(I) complex (TIMMNmes)CoI(BPh4) (2) (TIMMNmes=tris‐2‐(3‐mesitylimidazolin‐2‐ylidene)methylamine) with 1‐adamantylazide yields the cobalt(III) imido complex ...(TIMMNmes)CoIII(NAd)(BPh4) (3) with concomitant release of dinitrogen. The N‐anchor in diamagnetic 3 features an unusual, planar tertiary amine, which results from repulsive electrostatic interaction with the filled d(z2)‐orbital of the cobalt ion and negative hyperconjugation with the neighboring methylene groups. One‐electron oxidation of 3 with FeCp2(OTf) provides access to the rare, high‐valent cobalt(IV) imido complex (TIMMNmes)CoIV(NAd)(OTf)2 (4). Despite a half‐life of less than 1 h at room temperature, 4 could be isolated at low temperatures in analytically pure form. Single‐crystal X‐ray diffractometry and EPR spectroscopy corroborate the molecular structure and the d5 low‐spin, S=1/2
, electron configuration. A computational analysis of 4 suggests high covalency within the CoIV=NAd bond with non‐negligible spin density located at the imido moiety, which translates into substantial triplet nitrene character.
Straightforward access to a cobalt(IV) terminal imido complex was provided by one‐electron oxidation of a cobalt(III) terminal imido precursor. The cobalt(IV) monoimido complex could be isolated at low temperatures in analytically pure form. Single‐crystal X‐ray diffractometry and EPR spectroscopy corroborate the molecular structure and the d5 low‐spin, S=1/2
, electron configuration.
The synthesis, characterization, and reactivity of a series of cobalt terminal imido complexes supported by an N-anchored tripodal tris(carbene) chelate is described, including a Co-supported ...singlet nitrene. Reaction of the CoI precursor (TIMMNmes)CoI(PF6) (TIMMNmes = tris-2-(3-mesityl-imidazolin-2-ylidene)-methylamine) with p-methoxyphenyl azide yields a CoIII imide (TIMMNmes)CoIII(NAnisole)(PF6) (1). Treatment of 1 with 1 equiv of FeCp2(PF6) at −35 °C affords a formal CoIV imido complex (TIMMNmes)Co(NAnisole)(PF6)2 (2), which features a bent Co–N(imido)–C(Anisole) linkage. Subsequent one-electron oxidation of 2 with 1 equiv of AgPF6 provides access to the tricationic cobalt imido complex (TIMMNmes)Co(NAnisole)(PF6)3 (3). All complexes were fully characterized, including single-crystal X-ray diffraction (SC-XRD) analyses, infrared (IR) vibrational, ultraviolet/visible (UV/vis) electronic absorption, multinuclear NMR, X-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and high-energy-resolution fluorescence-detected X-ray absorption spectroscopy (HERFD XAS). Quantum chemical calculations provide additional insight into the electronic structures of all compounds. The dicationic CoIV imido complex 2 exhibits a doublet ground state with considerable imidyl character as a result of covalent Co–NAnisole bonding. At room temperature, 2 readily converts to a CoII amine complex involving intramolecular C–H bond amination. Electronically, tricationic complex 3 can be understood as a singlet nitrene bound to CoIII with significant CoIV imidyl radical character. Verifying the pronounced electrophilicity, nucleophiles such as H2O and t BuNH2 add to 3analogous to the parent free nitrenein the para position of the aromatic substituent, thus, clearly corroborating singlet nitrene-type reactivity.
A facile method for the electrodeposition of amorphous nickel oxyhydroxide is described and discussed in which well‐defined nickel complexes with pyridinedimethanol ligands are employed as ...single‐source molecular precursors. No buffering agent is required to assist the anodic deposition process. The deposited nickel oxyhydroxide shows high robustness and efficiency for electrocatalytic water oxidation.
NiOx for ox: Upon the application of an anodic potential, molecular nickel cubane 1 with 2,6‐pyridinedimethanol ligands is converted into amorphous nickel oxyhydroxide, which catalyzes water oxidation efficiently.
Two novel rhodium(III) complexes, namely, RhIII(X)Cl3 (X = 2 2,6-bis((4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine or ...2,6-bis((4S,7R)-1,7,8,8-tetramethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine), were synthesized from camphor derivatives of a bis(pyrazolylpyridine), tridentate nitrogen-donor chelate system, giving RhIII(H2L*)Cl3 (1a) and RhIII(Me2L*)Cl3 (1b). A rhodium(III) terpyridine (terpy) ligand complex, RhIII(terpy)Cl3 (1c), was also synthesized. By single-crystal X-ray analysis, 1b crystallizes in an orthorhombic P212121 system, with two molecules in the asymmetric unit. Tridentate coordination by the N,N,N-donor localizes the central nitrogen atom close to the rhodium(III) center. Compounds 1a and 1b were reactive toward l-methionine (l-Met), guanosine-5′-monophosphate (5′-GMP), and glutathione (GSH), with an order of reactivity of 5′-GMP > GSH > l-Met. The order of reactivity of the RhIII complexes was: 1b> 1a > 1c. The RhIII complexes showed affinity for calf thymus DNA and bovine serum albumin by UV–vis and emission spectral studies. Furthermore, 1b showed significant in vitro cytotoxicity against human epithelial colorectal carcinoma cells. Since the RhIII complexes have similar coordination modes, stability differences were evaluated by density functional theory (DFT) calculations (B3LYP(CPCM)/LANL2DZp). With (H2L*) and (terpy) as model ligands, DFT calculations suggest that both tridentate ligand systems have similar stability. In addition, molecular docking suggests that all test compounds have affinity for the minor groove of DNA, while 1b and 1c have potential for DNA intercalation.
The aim of the study was to investigate the complete substitution of imported soybean meal in beef cattle diets and the consequences on performance, meat, and adipose tissue quality. Thirty growing ...crossbred Limousin bulls, with an initial bodyweight of 164 ± 13 kg and 4.3 ± 0.3 months of age, were fed a grass/maize-silage based diet with little additional concentrate (0.5:0.3:0.2). Concentrates contained either soybean meal (positive control), faba beans, pumpkin seed cake, or spirulina (Arthrospira platensis), resulting in about 226 g crude protein (CP)/kg concentrate dry matter (DM) and 158 g CP/kg total diet DM. A grain-based concentrate providing just 135 g CP/kg concentrate DM and 139 g CP/total diet DM served as a negative control. Bulls of all groups had comparable average daily gains (1.43 ± 0.1 kg) and feed intakes (6.92 ± 0.37 kg). Carcass and meat quality did not differ among groups. The fatty acid profile of meat lipids was hardly affected. These results indicate that soybean meal can be replaced by any of the tested protein sources without impairing performance or meat quality. Importantly, bulls fed the negative control achieved a fattening and slaughter performance comparable to that of the protein-supplemented groups without affecting meat and adipose tissue quality. Thus, the present findings suggest that feeding crossbred bulls a grass/maize-silage based diet does not require additional protein supplementation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Starting from dimethyl 2,6-pyridinedicarboxylate (3), four pyridine-bridged bispyrazole ligands 1a-1d were generated in a two- or three-step synthesis sequence and further treated with UCl
to yield ...the corresponding novel mononuclear uranium(iv) complexes U
(R'''
L)(Cl)
(2a-2d). Compounds 2a-2d were characterized by a variety of spectroscopic and physical methods (e.g. UV/Vis, SQUID, CV, etc.), corroborating the +4 oxidation state in 2a-2d. Single-crystal X-ray structure analyses revealed that 2a·2THF crystallizes in the orthorhombic space group Pbca, 2b·0.8THF·0.2Et
O in the monoclinic Sohncke space group P2
, 2c·0.25Et
O in the monoclinic one P2
/c, and finally 2d·0.5THF in the orthorhombic Sohncke space group P2
2
2. In the solid state, complexes 2a-2d possess a distorted pentagonal-bipyramidal coordination sphere at the U
centers and an out-of-plane shift (d
) of up to 1.12 Å, which can be explained by an increased steric pressure on the metal ions at the binding sites of the chelating ligands 1c and 1d. Finally, by combination of different 1D and 2D NMR experiments, the
H and
C resonances can be unequivocally assigned in the corresponding paramagnetic NMR spectra of 2a-2d.
A novel rhodium(iii) complex Rh
(H
L
)Cl
(1) (H
L
= 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine) containing a pincer type, tridentate nitrogen-donor chelate system was synthesized. Single crystal ...X-ray structure analysis revealed that 1 crystallizes in the orthorhombic space group Pbcn with a = 20.7982(6), b = 10.8952(4), c = 10.9832(4) Å, V = 2488.80(15) Å
, and eight molecules in the unit cell. The rhodium center in the complex Rh
(H
L
)Cl
(1) is coordinated in a slightly distorted octahedral geometry by the tridentate N,N,N-donor and three chloro ligands, adopting a mer arrangement with an essentially planar ligand skeleton. Due to the tridentate coordination of the N,N,N-donor, the central nitrogen atom N1 is located closer to the Rh
center. The reactivity of the synthesized complex toward small biomolecules (l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), l-histidine (l-His) and glutathione (GSH)) and to a series of duplex DNAs and RNA was investigated. The order of reactivity of the studied small biomolecules is: 5'-GMP > GSH > l-Met > l-His. Duplex RNA reacts faster with the Rh
(H
L
)Cl
complex than duplex DNA, while shorter duplex DNA (15mer GG) reacts faster compared with 22mer GG duplex DNA. In addition, a higher reactivity is achieved with a DNA duplex with a centrally located GG-sequence than with a 22GTG duplex DNA, in which the GG-sequence is separated by a T base. Furthermore, the interaction of this metal complex 1 with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was examined by absorption (UV-Vis) and emission spectral studies (EthBr displacement studies). Overall, the studied complex exhibited good DNA and BSA interaction ability.
Within this paper is presented the synthesis and structural characterization of three newly synthesized osmium(
ii
) complexes
Os1-3
, with the chemical formula Os
II
LCl
2
H
2
O, L = 2,6-bis(5-
tert
...-butyl-1
H
-pyrazol-3-yl)pyridine (for
Os1
), 2,6-bis(5-
tert
-butyl-1-methyl-1
H
-pyrazol-3-yl)pyridine (for
Os2
) or 2,2′:6′,2′′-terpyridine (for
Os3
). Single crystal X-ray analysis of a DMSO adduct of complex
Os1
was performed. Kinetics of substitution reactions of examined
Os1-3
complexes with biomolecules 5-GMP,
l
-Met, and GSH were followed in the presence and absence of different biocompatible ionic liquids. Binding properties of the examined complexes to biologically important molecules, CT-DNA and HSA, were investigated using UV-Vis spectrophotometry, fluorescence spectroscopy, and gel electrophoresis. Interactions with CT-DNA were performed both in the absence and presence of biocompatible ionic liquids. To locate the binding site and possible binding mode of the examined complexes to CT-DNA and HSA, fluorescence competition experiments with site-markers were performed. To better understand these interactions and obtain detailed binding information of the examined complexes with CT-DNA, and HSA, molecular docking studies and fluorescence resonance energy transfer (FRET) were performed.
In vitro
cytotoxicity and redox status experiments on three cancer cell lines and on one healthy cell line were performed to elucidate the possible molecular mechanisms of investigated
Os1-3
complexes.
New bis(pyrazolylpyridine) Os(
ii
) complexes showing possible biological activity with diverse modes of action in the presence of biocompatible ionic liquids as non-toxic cosolvents for sparingly soluble complexes.
Easy come, easy go: The first molecular SO2 complexes of the lanthanides (Ln=Sm, Eu) have been prepared. The compounds can reversibly coordinate gaseous SO2. Concomitant with the addition and removal ...of SO2, the color of the complexes changes reversibly (see scheme). The structures of the SO2 compounds could be confirmed in solution and in the solid state.
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