Stereochemistry and chiroptical properties of bimetallic single helicates of hexapyrrole-α, ω-dicarbaldimines with high diastereoselectivity

2021 ◽  
pp. A-T
Author(s):  
Thi Hien Thuy Nguyen ◽  
Chaolu Eerdun ◽  
Takuya Okayama ◽  
Satoshi Hisanaga ◽  
Takumi Tominaga ◽  
...  
Keyword(s):  
Open Form ◽  
Closed Formula ◽  
Symmetric Form ◽  
Trans Conformation ◽  
Chiroptical Properties ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cation Radicals ◽  
Spectral Changes ◽  
Coordination Sites

Bimetallic complexes of hexapyrrole-[Formula: see text],[Formula: see text]-dicarbaldimines consisting of a pair of four-coordinate metal sites adopt a helical closed [Formula: see text]-symmetric form or sigmoidal open forms depending on whether the 2,2[Formula: see text]-bipyrrole subunit at the center of the hexapyrrole chain takes cis- or trans-conformation. X-ray crystallography of a bisNi complex having N-[([Formula: see text]-1-cyclohexylethyl]carbaldimine units at both ends of the hexapyrrole chain revealed a non-symmetric heterohelical open form where the metal coordination sites of opposite helical sense sit on opposite sides of the central 2,2[Formula: see text]-bipyrrole subunit. BisPd complexes preferred a closed [Formula: see text] form and a steric bulk at the 3,3[Formula: see text]-position of the 2,2[Formula: see text]-bipyrrole subunit improved the helical sense bias. A bisPd complex with N-[([Formula: see text]-1-cyclohexylethyl]carbaldimine units adopts a helical closed [Formula: see text] form exclusively with full bias for a [Formula: see text]-helical sense. These bimetallic single stranded helicates were reversibly oxidized to [Formula: see text]-cation radicals at 0.1[Formula: see text]0.3 V vs. a ferrocene/ferrocenium couple and spectroelectrochemistry revealed remarkable absorption and CD spectral changes in the Vis-NIR region.

New homodinuclear tris(3-alkylpyrazolyl)borate complexes of CoIIand NiIIwith a tetraacetylethane dianion as a bridging ligand

2016 ◽  
Vol 72 (11) ◽  
pp. 777-785
Author(s):  
Elena A. Mikhalyova ◽  
Swiatoslaw Trofimenko ◽  
Matthias Zeller ◽  
Anthony W. Addison ◽  
Vitaly V. Pavlishchuk
Keyword(s):  
Metal Ions ◽  
Coordination Polymers ◽  
Metal Ion ◽  
Molecular Structures ◽  
Polynuclear Complexes ◽  
X Ray ◽  
X Ray Crystallography ◽  
Coordination Sites ◽  
Borate Complexes ◽  
Capping Ligands

Polynuclear complexes and coordination polymers of 3dmetals have attracted significant interest evoked by a number of their unique properties. One of the most common approaches to the directed synthesis of coordination polymers is the linking of pre-prepared discrete coordination units by polydentate ligands. The formation of polynuclear complexes is usually a spontaneous process and precise prediction of the products of such reactions is virtually impossible in most cases. Tris(pyrazolyl)borates (Tp) act as tripodal `capping' ligands which form stable complexes with 3dmetal ions. In such 1:1 compounds, three metal-ion coordination sites are occupied by N atoms from a Tp anion. This limits the number of remaining coordination sites, and thus the number of additional ligands which may coordinate, and opens an attractive approach for the directed design of desirable structures by exploiting ligands with appropriate composition and topology. In the present study, Tp anions with neopentyl [TpNp, tris(3-neopentylpyrazolyl)borate] and cyclohexyl [TpCy, tris(3-cyclohexylpyrazolyl)borate] substituents were used as `capping' ligands and the dianion of tetraacetylethane (3,4-diacetylhexa-2,4-diene-2,5-diolate, tae2−) was employed as a bridge. The dinuclear complexes (μ-3,4-diacetylhexa-2,4-diene-2,5-diolato-κ4O2,O3:O4,O5)bis{[tris(3-cyclohexyl-1H-pyrazol-1-yl-κN2)borato]cobalt(II)} acetonitrile disolvate, [Co2(C27H40BN6)2(C10H12O4)]·2CH3CN, (I)·2CH3CN, and (μ-3,4-diacetylhexa-2,4-diene-2,5-diolato-κ4O2,O3:O4,O5)bis{[tris(3-neopentyl-1H-pyrazol-1-yl-κN2)borato]nickel(II)}, [Ni2(C24H40BN6)2(C10H12O4)], (II), were synthesized by the reaction of the mononuclear complexes TpCyCoCl or TpNpNiCl with H2tae (3,4-diacetylhexane-2,5-dione or tetraacetylethane) in the presence of NEt3as base. Compounds (I) and (II) were characterized by mass spectrometry, elemental analysis, and X-ray crystallography. They possess similar molecular structures, X-ray diffraction revealing them to be dinuclear in nature and composed of discrete Tp–Munits in which two metal ions are linked by a tae2−dianion. Each metal ion possesses a five-coordinate square-pyramidal environment. The interplanar angles between the acetylacetonate fragments are significantly smaller than the near-90° values commonly observed.

Vicinal-diaryl interactions in stilbenoid hydrocarbons as observed in the through-space charge delocalization of their cation radicals

1999 ◽  
Vol 77 (5-6) ◽  
pp. 913-921 ◽  
Author(s):  
Rajendra Rathore ◽  
Jay K Kochi
Keyword(s):  
Space Charge ◽  
Cation Radical ◽  
Conformational Preference ◽  
Charge Delocalization ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cation Radicals ◽  
Near Ir ◽  
Aromatic Interactions ◽  
Vis Spectroscopy

The conformational preference of vicinal or 1,2-phenyl groups is probed in two classes of ring-substituted 1,2-diphenylbicyclooctene (stilbenoid) hydrocarbons 1a-1d and 2a-2c. UV-vis spectroscopy reveals, and X-ray crystallography verifies, the intramolecular (edge-to-face) orientation for the phenyl-phenyl interaction in stilbenoids 1a-1d. Most importantly, when two pairs of ortho-methyl substituents are present, the cofacial phenyl groups in the stilbenoid donors are established by X-ray crystallography and spectrally observed in the cation radicals (2a+.-2c+.) by the appearance of new bands with strong absorptions in the near IR with λmax = 1100-1315 nm, analogous to those previously observed in intermolecular (aromatic) interactions of aromatic cation radicals.Key words: stilbenoid hydrocarbon, cation radical, aryl-aryl interaction.

Interpenetrated Double Pillared-Layer CoII MOFs with pcu Topology

2017 ◽  
Vol 70 (5) ◽  
pp. 461 ◽  
Author(s):  
In-Hyeok Park ◽  
Yunji Kang ◽  
Eunji Lee ◽  
Anjana Chanthapally ◽  
Shim Sung Lee ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Layer Structure ◽  
Metal Organic Frameworks ◽  
Trans Conformation ◽  
X Ray ◽  
Pore Sizes ◽  
X Ray Crystallography ◽  
Metal Organic

Three double pillared-layer CoII metal–organic frameworks (MOFs) with a pcu topology of a long, conformationally flexible, dipyridyl spacer ligand, 1,4-bis[2-(4-pyridyl)ethenyl]benzene (bpeb), and aromatic dicarboxylates (1,4-benzenedicarboxylate (bdc), 2,6-naphthalenedicarboxylate (ndc), and biphenyl-4,4′-dicarboxylate (bpdc)) have been synthesised and structurally characterised by X-ray crystallography. The MOFs are denoted as [Co2(bpeb)2(bdc)2]·DMF·3H2O (1), [Co2(bpeb)2(ndc)2]·1.75DMF·3.75H2O (2), and [Co2(bpeb)2(bpdc)2]·3.5DMF·4H2O (3). In the dinuclear repeating unit, four carboxylates are bonded to two CoII atoms forming a (4,4) layer structure. The axial positions are occupied by bpeb ligands. Of these, 1 and 2 have 2-fold interpenetration, whereas 3 displays 3-fold interpenetration. The two bpeb space ligands in 1 have trans,trans,trans and trans,cis,trans conformations. In contrast, the bpeb ligands in 2 and 3 have a trans,cis,trans conformation. Although the olefin groups in two adjacent bpeb ligands, as the double pillars in 2 and 3, satisfy the conditions for photo-dimerisation to occur, they are photo-inactive. The conformational changes of bpeb, bonding modes of the dicarboxylates, and pore sizes in these double pillared-layer compounds have been discussed.

scholarly journals Isolation of a chiral anthracene cation radical: X-ray crystallography and computational interrogation of its racemization

2017 ◽  
Vol 53 (18) ◽  
pp. 2748-2751 ◽  
Author(s):  
Maxim V. Ivanov ◽  
Khushabu Thakur ◽  
Anshul Bhatnagar ◽  
Rajendra Rathore
Keyword(s):  
Charge Transfer ◽  
Dft Calculations ◽  
Cation Radical ◽  
Enantioselective Synthesis ◽  
X Ray ◽  
X Ray Crystallography ◽  
Anthracene Derivative ◽  
Cation Radicals ◽  
Radical Salt ◽  
Charge Transfer Materials

Chiral cation-radicals hold significant promise as charge-transfer materials, chiroptical switches, and catalysts for enantioselective synthesis. Herein we identify a chiral anthracene derivative that forms a robust cation-radical salt as established by X-ray crystallography and DFT calculations.

Probing Charge Delocalization in Solid State Polychromophoric Cation Radicals Using X-ray Crystallography and DFT Calculations

2018 ◽  
Vol 122 (17) ◽  
pp. 9339-9345 ◽  
Author(s):  
Lena V. Ivanova ◽  
Denan Wang ◽  
Sergey Lindeman ◽  
Maxim V. Ivanov ◽  
Rajendra Rathore
Keyword(s):  
Solid State ◽  
Dft Calculations ◽  
Charge Delocalization ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cation Radicals

scholarly journals On the Development of Selective Chelators for Cadmium: Synthesis, Structure and Chelating Properties of 3-((5-(trifluoromethyl)-1,3,4-thiadiazol-2-yl)amino)benzo[d]isothiazole 1,1-dioxide, a Novel Thiadiazolyl Saccharinate

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1501
Author(s):  
Joana F. Leal ◽  
Bruno Guerreiro ◽  
Patrícia S. M. Amado ◽  
André L. Fernandes ◽  
Luísa Barreira ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Single Crystal ◽  
Toxic Metals ◽  
Chelating Agent ◽  
Negative Consequences ◽  
X Ray ◽  
X Ray Crystallography ◽  
Spectral Changes ◽  
Aquatic Contamination

Aquatic contamination by heavy metals is a major concern for the serious negative consequences it has for plants, animals, and humans. Among the most toxic metals, Cd(II) stands out since selective and truly efficient methodologies for its removal are not known. We report a novel multidentate chelating agent comprising the heterocycles thiadiazole and benzisothiazole. 3-((5-(trifluoromethyl)-1,3,4-thiadiazol-2-yl)amino)benzo[d]isothiazole 1,1-dioxide (AL14) was synthesized from cheap saccharin and characterized by different techniques, including single crystal X-ray crystallography. Our studies revealed the efficiency and selectivity of AL14 for the chelation of dissolved Cd(II) (as compared to Cu(II) and Fe(II)). Different spectral changes were observed upon the addition of Cd(II) and Cu(II) during UV-Vis titrations, suggesting different complexation interactions with both metals.

[Ni5(SEt)10] und [Ni4(SC6H11)8], homoleptische Nickel-Thiolate mit pentagonal-prismatischen und cubanartigen Schwefelgerüsten /[Ni5(SEt)10] and [Ni4(SC6H11)8], Homoleptic Nickel-Thiolates with Pentagonal-Prismatic and Cubane-Like Sulfur Frameworks

1987 ◽  
Vol 42 (9) ◽  
pp. 1121-1128 ◽  
Author(s):  
Michael Kriege ◽  
Gerald Henkel
Keyword(s):  
Methylene Chloride ◽  
Methanol Solution ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Coordination Sites ◽  
Square Planar ◽  
Solvent Molecules

NiCl2 reacts with NaSR in methanol solution to give the black diamagnetic complexes [Ni5(SR)10] (R = Et, 1) and [Ni4(SR)8] (R = C6H11 , 2). Crystals of 1 are monoclinic, space group P21/h with a = 13.149(4), b = 15.571(4), c = 17.917(5) Å , β = 105.31(2)° and Z = 4. 2 crystallizes from methylene chloride with sixteen solvent molecules per unit cell in the orthorhombic space group Ibca with a = 17.902(8), b = 18.289(8), c = 37.99(2) Å and Z = 8. The structures of 1 and [Ni4(SC6HM)8] · 2 CH 2Cl2 (3) have been determined by X-ray crystallography and refined to R(RW) = 0.072 (0.062) and 0.119 (0.128), respectively. Both complexes are cyclic neutral molecules and contain square planar NiS4 coordination sites (1: mean Ni - S 2.200 Å , mean S -Ni -S 81.8 ( 2 x ) . 98.3 ( 2 x ) , 170.8° ( 2 x ) ; 2: mean Ni - S 2.213 Å , mean S - Ni - S 80.9 (2 x ) , 98.2 ( 2 x ) , 167.5°(2 x )) condensed via opposite edges. A s a result, prismatic sulfur frameworks are observed which are pentagonal in the case of 1 and tetragonal in the case of 2. Their lateral faces are centered by Ni atoms. The symmetry of the Ni-S core portion approaches D5h for 1 and D4h for 2. With reference to the toroidal N i-S frameworks, the sulfur-carbon bonds of each pair of opposite ligands are in axial and equatorial positions, respectively. This configuration alternates around the prismatic sulfur arrangement which is completely compatible with the even number of nickel atoms present in 2, but results in a node for 1 due to the five-fold symmetry.

X-ray Crystallography and Unexpected Chiroptical Properties Reassign the Configuration of Haliclonadiamine

2020 ◽  
Vol 142 (6) ◽  
pp. 2755-2759 ◽  
Author(s):  
Hong-Bing Liu ◽  
Gregory H. Imler ◽  
Kim K. Baldridge ◽  
Robert D. O’Connor ◽  
Jay S. Siegel ◽  
...  
Keyword(s):  
Chiroptical Properties ◽  
X Ray ◽  
X Ray Crystallography

scholarly journals Crystal structure analysis and supramolecular association in ethyl N-[amino(iminio)methyl]carbamate dichloride hemi-hydrate

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Christiana Bamigboye ◽  
Hanna S. Abbo ◽  
Huey Chong Kwong ◽  
Sang Loon Tan ◽  
Edward R.T. Tiekink ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Electrostatic Potential ◽  
Positive Charge ◽  
Crystal Structure Analysis ◽  
Relative Orientation ◽  
Asymmetric Unit ◽  
Trans Conformation ◽  
Crystal Water ◽  
X Ray ◽  
X Ray Crystallography

Abstract X-ray crystallography on [EtOC(=O)N(H)C(=N+H2)NH2]Cl·½H2O (1) shows the asymmetric unit to comprise two independent cations, two chloride anions and crystal water. The main conformational difference between the cations is seen in the relative orientation of the ethyl groups; geometry-optimisation confirms the all-trans conformation is the most stable. The remaining parts of the cations are co-planar and feature intramolecular N–H···O(carbonyl) hydrogen bonds. An analysis of the C–N bonds suggests substantial delocalisation of the positive charge over the CN3 atoms. In the crystal, columns comprising the first independent cation are surrounded by four columns of the second cation within a network of water-O–H···Cl, N–H···Cl and N–H···O(water, carbonyl) hydrogen bonds, many of which are charge-assisted. The packing has been further investigated by Hirshfeld surface analysis, molecular electrostatic potential and interaction energy calculations. The charge-assisted N–H···Cl hydrogen bonds are significantly stronger than the water-O–H···Cl interactions consistent the distribution of the positive charge over the CN3 atoms.

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