Complexation reactions of palladium(II) nitrate with a set of 3-pyridyl appended nonchelating bidentate ligands possessing regioisomeric phenylene-diurea functionalities as spacers were carried out. The ligands utilized in this study are 1,1′-(1,2-phenylene)bis(3-(pyridin-3-yl)urea), L1; 1,1′-(1,3-phenylene)bis(3-(pyridin-3-yl)urea), L2; and 1,1′-(1,4-phenylene)bis(3-(pyridin-3-yl)urea), L3. The complexation reactions of the ligands (L1, L2, and L3) with palladium(II) produced single discrete isomeric cages (1, 2, and 3) of Pd 2 L 4 formulation in each case and thereby illustrated ligand-isomerism in coordination cages. All 16 hydrogen atoms of eight urea moieties present in four ligand strands are delineated completely endohedrally in cage 1 and completely exohedrally in cage 3, whereas cage 2 exhibited half of the urea hydrogens in exohedral locations and the remaining half in endohedral locations. In addition to the variable number of solvent molecules, the cavities of cages 1 and 2 lodged four and two nitrate ions, respectively, using the endohedral (H) urea atoms (i.e., NH groups) as binding sites, whereas the cavity of 3 remained anion free. The abilities of the complexes 1-3 for adsorption of CO 2 gas are demonstrated, and their behaviors are compared. Copyright © 2018 American Chemical Society.

Dillip Kumar Chand

Department Of Chemistry

Hareesha Dasary

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

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IIT Madras

Inorganic Chemistry

The complexation study of cis-protected and bare palladium(II) components with a new tridentate ligand, i.e., pyridine-3,5-diylbis(methylene) dinicotinate (L1) is the focus of this work. Complexation of cis-Pd(tmeda)(NO3)2 with L1 at a 1:1 or 3:2 ratio produced [Pd(tmeda)(L1)](NO3)2 (1a). The reaction mixture obtained at 3:2 ratio upon prolonged heating, produced a small amount of [Pd3(tmeda)3(L1)2](NO3)6 (2a). Complexation of Pd(NO3)2 with L1 at a 1:2 or 3:4 ratios afforded [Pd(L1)2](NO3)2 (3a) and [(NO3)2@Pd3(L1)4](NO3)4 (4a), respectively. The encapsulated NO3- ions of 4a undergo anion exchange with halides (F-, Cl- and Br- but not with I-) to form [(X)2@Pd3(L1)4](NO3)4 5a-7a. The coordination behaviour of ligand L1 and some dynamic properties of these complexes are compared with a set of known complexes prepared using the regioisomeric ligand bis(pyridin-3-ylmethyl)pyridine-3,5-dicarboxylate (L2). Importantly, a ligand isomerism phenomenon is claimed by considering complexes prepared from L1 and L2. © 2019 Samantray et al.

Fulltext

Beilstein Journal of Organic Chemistry

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

A series of Pd2L4-type binuclear self-assembled coordination cages (1–4), where L stands for a nonchelating bidentate ligand, were prepared. The strategies adopted for the synthesis of the cages were: combination of PdIIwith 1) a selected ligand or 2) subcomponents of the ligand. Highly efficient cage-to-cage transformation reactions are demonstrated by suitable covalent modification (from 1 to 2 or 3 or 4) or ligand-exchange reactions (from 1 to 2 or 3 or 4; from 2 to 3 or 4). Thus, new cascade transformations (from 1 to 2 to 3; from 1 to 2 to 4) are achieved beautifully. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Chemistry - A European Journal

Cage-to-Cage Cascade Transformations

A rare variety of coordination rings having the M<inf>3</inf>L<inf>6</inf> composition are prepared by the combination of Pd(NO<inf>3</inf>)<inf>2</inf> with an imidazolyl or benzimidazolyl appended bidentate non-chelating ligand (i.e.L1 or L2). The variable concentration 1H NMR spectra of the trinuclear complexes [Pd<inf>3</inf>(L1)<inf>6</inf>](NO<inf>3</inf>)<inf>6</inf>, 1a and [Pd<inf>3</inf>(L2)<inf>6</inf>](NO<inf>3</inf>)<inf>6</inf>, 2a in DMSO-d<inf>6</inf> provided valuable information on the self-assembly phenomenon of the already self-assembled complexes. Interestingly, the signals of 2a are broadened upon increasing the concentration. The solution of 2a in DMSO formed a supramolecular metallogel above a certain concentration (i.e. 2% w/v), however, complex 1a could not form any gel. This phenomenon is attributed to the presence of an auxiliary π-surface in the benzimidazole moiety in L2, in contrast to the imidazole moiety of L1. The influence of anions in gel formation was studied by preparing several samples using a variety of palladium(ii) salts and L2 in DMSO. It was found that oxoanions like nitrate, perchlorate, triflate and tosylate are amicable for gel formation, probably due to their capabilities of forming H-bonds. The counter anions like tetrafluoroborate, hexafluorophosphate, or hexafluoroantimonate could not assist in the formation of gel. The stimuli-responsive nature of the gel and the reversible gel-sol conversion were demonstrated by dis-assembly and re-assembly processes of 2a as controlled by a pair of stimuli such as halide-nitrate, DMAP-HNO<inf>3</inf>, and ethylenediamine-Pd(NO<inf>3</inf>)<inf>2</inf>. No gel could be prepared by the combination of Ni(NO<inf>3</inf>)<inf>2</inf> or Pt(NO<inf>3</inf>)<inf>2</inf> with ligand L2. Thus, a subtle change in the ligand design, metal ion and counter anion is demonstrated as the responsible parameter for the construction of the three component multi-stimuli-responsive supramolecular gel. © The Royal Society of Chemistry 2015.

Dalton Transactions

Nanoscale metallogel via self-assembly of self-assembled trinuclear coordination rings: Multi-stimuli-responsive soft materials

A series of self-assembled "double saddle"-type trinuclear complexes of [Pd3L′3L3] formulation have been synthesized by complexation of a series of cis-protected palladium(II) components with a slightly divergent "Eshaped" non-chelating tridentate ligand, 1,1′-(pyridine-3,5-diyl)bis(3-(pyridin-3-yl)urea (L). The cis-protecting agents L′ employed in the study are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen), for 1, 2, 3, and 4, respectively. The crystal structures of [Pd3(tmeda)3(L)2](NO3)6 (2), [Pd3(bpy)3(L)3](NO3)3 (3), and [Pd3(phen)3(L)2](NO3 )6 (4) unequivocally support the new architecture. Two of the "double saddle"-type complexes (3 and 4) are suitably crafted with p surfaces at the strategically located cis-protecting sites to facilitate intermolecular p-p interactions in the solid state. As a consequence, six units of the 3 (or 4 ) are assembled, by means of six-pairs of p-p stacking interactions, in a circular geometry to form an octadecanuclear molecular ring of [(Pd3L′3L3)3] composition. The overall arrangement of the rings in the crystal packing is equated with the traditional Indian art form rangoli. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Octadecanuclear gear wheels by self-assembly of self-assembled "double saddle"-type coordination entities: Molecular "rangoli"

Palladium(II) has four coordination sites and forms square planar complexes. Discrete self-assemblies are generated by the combination of a variety of palladium(II) components and ligands ranging from bi- to polydentate. The Pd(II) components used are generally of two varieties: cis-protected Pd(II) and unprotected Pd(II). Most common cis-protecting units (X-X) such as ethylenediamine, 2,2'-bipyridine and 1,3-bis(diphenylphosphino)propane and a few other related chelating systems have been exploited for the complexation reactions. The self-assemblies formed are generally represented as [{cis-Pd(X-X)} x(L) y](monoanion) 2x and [Pd m(L) n](monoanion) 2m when generated from the complexation of a suitable ligand (L) with cis-protected Pd(II) and simple Pd(II) units, respectively. When Pd(solvent) 2Cl 2 is complexed with ligands, the solvent molecules are replaced with the incoming ligands, leading to complexes in which the trans positions are occupied by the chloride anions. © 2012 Elsevier B.V.

Coordination Chemistry Reviews

Self-assembled coordination complexes from various palladium(II) components and bidentate or polydentate ligands

Self-assembled binuclear coordination cages of general formula [Pd 2(N-N)2(L)2](X)4, 1a/b-4a/b are prepared by the combination of N,N′-bis(m-pyridyl)urea, L, with a variety of cis-protected palladium(II) components, Pd(N-N)(X)2. The cis-protecting units "N-N" employed for the synthesis of 1-4 are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen), respectively. The term "X" stands for nitrate and perchlorate for a and b, respectively. The assemblies are characterized by NMR and electrospray ionization mass spectrometry (ESI-MS) techniques, and in some cases (i.e., 1a, 2b, 3b, 4a, and 4b) the structures are confirmed by single crystal X-ray diffraction. The conformations of bound L in the crystal structures of all the Pd(II) complexes are found to be syn-syn. The influence of the presence and absence of π cloud at the cis-protecting units on the crystal packing has been studied in detail. In the packing of [Pd 2(phen)2L2](NO3)4, 4a, one unit of [Pd2(phen)2L2]4+ is associated with two other units by π-π stacking interactions thus giving a one-dimensional growth as envisioned on the basis of a design principle. In the case of [Pd2(en)2(L)2](NO3) 4, 1a, and [Pd2(tmeda)2(L)2] (ClO4)4, 2b, such packing is not observed due to the absence of π-cloud at the strategic locations, instead notable H-bonding interactions are seen. However, [Pd2(bpy)2(L) 2](ClO4)4, 3b, displays a π-π interactions using only two units of [Pd2(bpy)2(L) 2]4+(ClO4)-. © 2012 American Chemical Society.

Crystal Growth and Design

Consequence of presence and absence of π-clouds at strategic locations of designed binuclear Pd(II) complexes on packing: Self-assembly of self-assembly by intermolecular locking and packing

Journal	Data powered by TypesetInorganic Chemistry
Publisher	Data powered by TypesetAmerican Chemical Society
ISSN	00201669
Open Access	No