A New Structural Motif for an Enantiomerically Pure Metallosupramolecular Pd4L8 Aggregate by Anion Templating

An enantiomerically pure BINOL‐based bis(3‐pyridyl) ligand 1 assembles into a homochiral [Pd₄( 1 )₈] complex upon coordination to tetravalent Pd^II ions. The formation of this aggregate is templated by two tetrafluoroborate counterions that are encapsulated in two peripheral cavities. The resulting structure is a new structural motif for this kind of metallosupramolecular assemblies that arranges the palladium ions in a distorted tetrahedral fashion and forces ligand 1 to adopt two different conformations. Both phenomena are unique and cause an overall three‐dimensional structure that has another confined, chiral, and hydrophilic central cavity.     

Unexpected Self‐Assembly of a Homochiral Metallosupramolecular M4L4 Catenane

Two enantiomerically pure 9,9′‐spirobifluorene‐based bis(pyridine) ligands 1 and 2 were prepared to study their self‐assembly behavior upon coordination to cis‐protected palladium(II) ions. Whereas the sterically more demanding ligand, 2 , gave rise to the expected dinuclear metallosupramolecular M₂L₂ rhombi, the sterically less demanding ligand, 1 , acts as a template to give rise to a homochiral metallosupramolecular M₄L₄ catenane.     

Self-Assembly of a Redox Active,Metallosupramolecular [Pd3L6]6+ Complex Using a Rotationally Flexible Ferrocene Ligand

A new ferrocene-containing [Pd₃( L_4EFc )₆]⁶⁺(X⁻)₆ ( C ⋅ BF₄ and C ⋅ SbF₆ where X=BF₄⁻ or SbF₆⁻) self-assembled double-walled triangle has been synthesized from the known, rotationally flexible, 1,1′-bis(4-pyridylethynyl)ferrocene ligand ( L_4EFc ), and characterized by ¹H, ¹³C and diffusion ordered (DOSY) NMR spectroscopies, high-resolution electrospray ionization mass spectrometry (HR−ESI−MS), X-ray crystallography and cyclic voltammetry (CV). The molecular structures confirmed that double-walled triangle cage systems ( C ⋅ BF₄ and C ⋅ SbF₆ ) were generated. C ⋅ BF₄ was shown to interact with the anionic guest, p-toluenesulfonate. CV experiments revealed that the triangles were redox active, however addition of the guest did not influence the redox potentials.     

An Octanuclear Metallosupramolecular Cage Designed To Exhibit Spin‐Crossover Behavior

By employing the subcomponent self‐assembly approach utilizing 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin or its zinc(II) complex, 1H ‐4‐imidazolecarbaldehyde, and either zinc(II) or iron(II) salts, we were able to prepare O‐symmetric cages having a confined volume of ca. 1300 ų. The use of iron(II) salts yielded coordination cages in the high‐spin state at room temperature, manifesting spin‐crossover in solution at low temperatures, whereas corresponding zinc(II) salts led to the corresponding diamagnetic analogues. The new cages were characterized by synchrotron X‐ray crystallography, high‐resolution mass spectrometry, and NMR, Mössbauer, IR, and UV/Vis spectroscopy. The cage structures and UV/Vis spectra were independently confirmed by state‐of‐the‐art DFT calculations. A remarkably high‐spin‐stabilizing effect through encapsulation of C₇₀ was observed. The spin‐transition temperature T _1/2 is lowered by 20 K in the host–guest complex.     

Two Succinato‐bridged Zinc(II) Phenanthroline Complexes: [Zn(phen)L2/2](H2L) and [(phen)2Zn(μ‐L)Zn(phen)2]L � 11H2O with H2L = Succinic Acid

Two mixed ligand Zn^II complexes [Zn(phen)L_2/2](H₂L) ( 1 ) and [(phen)₂Zn(μ‐L)Zn(phen)₂]L � 11H₂O ( 2 ) with H₂L = suc‐cinic acid were prepared and crystallographically characterized. Complex 1 crystallizes in the monoclinic space group C2/c (no. 15) with a = 13.618(1) Å, b = 9.585(1) Å, c = 15.165(1) Å, β = 96.780(6)°, V = 1965.6(3)ų, Z = 4 and complex 2 in the triclinic space group P 1¯ (no. 2) with a = 12.989(2)Å, b = 14.464(2)Å, c = 18.025(3)Å, α = 90.01(1)°, β = 109.69(1)°, γ = 112.32(1)°, V = 2917.4(8) ų, Z = 2. 1 consists of succinic acid molecules and 1D zigzag [Zn(phen)(C₄H₄O₄)_2/2] polymeric chains, in which the tetrahedrally coordinated Zn atoms are bridged by bis ‐ monodentate succinato ligands. Succinic acid molecules play an important role in supramolecular assemblies of the polymeric chains into 2D layers as well as in the stacking of 2D layers. 2 is composed of [(phen)₂Zn(μ‐L)Zn(phen)₂]²⁺ complex cations, succinate anions and hydrogen bonded water molecules. Within the divalent cations, Zn atoms are octahedrally coordinated by four N atoms of two phen ligands and two O atoms of one bis‐chelating succinato ligand. Through the intermolecular π—π stacking interactions, the complex cations form positively charged 2D layers, between which the noncoordinating succinate anions and water molecules are sandwiched.     

Quantitative Analysis of the Self‐Assembly Process of a Pd12L24 Coordination Sphere

The self‐assembly process of a Pd₁₂L₂₄ sphere was revealed by a quantitative approach (quantitative analysis of self‐assembly process: QASAP) quantifying all the substrates, the products, and the observable intermediates, indicating that the Pd₁₂L₂₄ sphere is produced through several pathways. Firstly, Pd_n L_2n (n= 6, 8, and 9), which are perfectly closed structures smaller than the Pd₁₂L₂₄ sphere, and a mixture of intermediates not observed by NMR ( Int ) were produced. Next, the sphere was assembled from intra‐/intermolecular reaction of a certain class of Int (path A) and from the coordination of free pyridyl groups in Int to the Pd^II center of Pd_n L_2n (n= 6, 8, and 9) (path B). While capping the free pyridyl groups in Int with Pd^II ions perfectly inhibited the sphere formation, the addition of free L to Int accelerated the formation of the sphere.     

A Double Cation–π‐Driven Strategy Enabling Two‐Dimensional Supramolecular Polymers as Efficient Catalyst Carriers

The cation–π interaction is a strong non‐covalent interaction that can be used to prepare high‐strength, stable supramolecular materials. However, because the molecular plane of a cation‐containing group and that of aromatic structure are usually perpendicular when forming a cation–π complex, it is difficult to exploit the cation–π interaction to prepare a 2D self‐assembly in which the molecular plane of all the building blocks are parallel. Herein, a double cation–π‐driven strategy is proposed to overcome this difficulty and have prepared 2D self‐assemblies with long‐range ordered molecular hollow hexagons. The double cation–π interaction makes the 2D self‐assemblies stable. The 2D self‐assemblies are to be an effective carrier that can eliminate metal‐nanoparticle aggregation. Such 2D assembly/palladium nanoparticle hybrids are shown to exhibit recyclability and superior catalytic activity for a model reaction.     

Two‐Component Self‐Assembly: Hierarchical Formation of pH‐Switchable Supramolecular Networks by π–π Induced Aggregation of Ion Pairs

Two‐component self‐assembly is a promising approach to construct functional nanomaterials. Interaction of a flexible guanidiniocarbonyl pyrrole tetra‐cation ( 1 ) with naphthalene diimide dicarboxylic acid (NDIDC) in aqueous DMSO leads to the formation of supramolecular networks. First, the carboxylate groups of NDIDC bind to the guanidiniocarbonyl pyrrole cations of 1 in a 1:2 stoichiometry. Further π–π induced aggregation then leads to 3D networks, as established by dynamic light scattering studies (DLS), NMR, fluorescence titration, viscosity measurements, AFM, and TEM microscopy. Due to ion pairing, the resulting aggregates can be switched between the monomers and the aggregates reversibly using external stimuli like protonation or deprotonation. At high concentration, a stable colloidal solution is formed, which shows an extensive Tyndall effect. Increasing the concentrations even further leads to formation of a supramolecular gel.     

Synthesis and Structural Characterization of ZnII α‐Diimine Complexes with Chloride and Thiocyanate Co‐Ligands

The preparation and spectroscopic and structural characterization of three Zn^II complexes with bis[N‐(2,6‐dimethylphenyl)imine]acenaphthene, L¹, and with bis[N‐(2‐ethylphenyl)imine]acenaphthene, L², are decribed herein. Two of the complexes were prepared from ZnCl₂ and the third from Zn(NCS)₂. One‐pot reaction techniques were used, leading to high yields. The complexes were characterized by microanalysis, IR and ¹H NMR spectroscopy, and single‐crystal X‐ray diffraction. The structures of the complexes are significantly different, with the chloride‐containing species forming distorted tetrahedra around the metal, whereas its thiocyanate analog is dimeric, with each metal at the center of a distorted square pyramid, with bridging and terminal [SCN]^– ligands.     

Interplay between H‐Bonding and Preorganization in the Evolution of Self‐Assembled Systems

Cooperative π–π interactions and H‐bonding are frequently exploited in supramolecular polymerization; however, close scrutiny of their mutual interplay has been largely unexplored. Herein, we compare the self‐assembly behavior of a series of C₂‐ and C₃‐symmetrical oligophenyleneethynylenes differing in their amide topology (N‐ or C‐centered). This subtle structural modification brings about drastic changes in their photophysical and supramolecular properties, highlighting the reciprocal impact of H‐bonding vs. preorganization on the evolution and final outcome of supramolecular systems.     

A Zipper‐like Supramolecular Double‐Chain based on 1 D π‐π Stacking Interactions: Synthesis and Crystal Structure of [Cu(phen)(C4H4O4)(H2O)]2 · C4H6O4 (phen = 1,10‐phenanthroline)

[Cu(C₁₂H₈N₂)(C₄H₄O₄)(H₂O)]₂ · C₄H₆O₄ was prepared by the reaction of succinic acid, CuCl₂ · 2 H₂O, 1,10‐phenanthroline (phen = C₁₂H₈N₂), and Na₂CO₃ in a CH₃OH–H₂O solution. The crystal structure (triclinic, P 1 (no. 2), a = 7.493(1), b = 9.758(1), c = 13.517(1) Å; α = 68.89(1)°, β = 88.89(1)°, γ = 73.32(1)°, Z = 1, R = 0.0308, wR² = 0.0799 for 3530 observed reflections (F ≥ 2σ(F ) out of 3946 unique reflections) consists of hydrogen bonded succinic acid molecules and succinato bridged 1 D zipperlike supramolecular [Cu(phen)(C₄H₄O₄)_2/2(H₂O)]₂ double chains based on 1 D π‐π stacking interactions between the chelating phen systems at distances of 3.71 Å and 3.79 Å. The Cu atoms are fivefold trigonal bipyramidally coordinated by two N atoms of the bidentate chelating phen ligand and three O atoms of one water molecule and two bidentate bridging succinate ligands. The water O atom and one phen N atom are at the apical positions (equatorial: d(Cu–O) = 1.945, 2.254(2) Å, d(Cu–N) = 2.034(2) Å; axial: d(Cu–O) = 1.971(2) Å, d(Cu–N) = 1.995 Å).     

Substitution‐Pattern‐ and Counteranion‐Depending Ion‐Pairing Assemblies Based on Electron‐Deficient Porphyrin–AuIII Complexes

Porphyrin–Au^III complexes, which were partially or totally modified with C₆F₅ at the meso positions, were synthesized. The highly electron‐withdrawing substituents induced electron‐deficient states and Lewis acid properties. Single‐crystal X‐ray analysis of the ion pairs revealed ion‐pairing assemblies with characteristics dependent on the number and substitution pattern of the C₆F₅ units and the geometries of the anions.     

Two Novel CuII Phenanthroline Adipato Complexes with π‐π Stacking Interactions: [Cu(phen)2(C6H8O4)] · 4.5 H2O and [(Cu2(phen)2Cl2)(C6H8O4)] · 4 H2O

The blue copper complex compounds [Cu(phen)₂(C₆H₈O₄)] · 4.5 H₂O ( 1 ) and [(Cu₂(phen)₂Cl₂)(C₆H₈O₄)] · 4 H₂O ( 2 ) were synthesized from CuCl₂, 1,10‐phenanthroline (phen) and adipic acid in CH₃OH/H₂O solutions. [Cu(phen)₂‐ (C₆H₈O₄)] complexes and hydrogen bonded H₂O molecules form the crystal structure of ( 1 ) (P1 (no. 2), a = 10.086(2) Å, b = 11.470(2) Å, c = 16.523(3) Å, α = 99.80(1)°, β = 115.13(1)°, γ = 115.13(1)°, V = 1617.5(5) ų, Z = 2). The Cu atoms are square‐pyramidally coordinated by four N atoms of the phen ligands and one O atom of the adipate anion (d(Cu–O) = 1.989 Å, d(Cu–N) = 2.032–2.040 Å, axial d(Cu–N) = 2.235 Å). π‐π stacking interactions between phen ligands are responsible for the formation of supramolecular assemblies of [Cu(phen)₂(C₆H₈O₄)] complex molecules into 1 D chains along [111]. The crystal structure of ( 2 ) shows polymeric [(Cu₂(phen)₂Cl₂)(C₆H₈O₄)_2/2] chains (P1 (no. 2), a = 7.013(1) Å, b = 10.376(1) Å, c = 11.372(3) Å, α = 73.64(1)°, β = 78.15(2)°, γ = 81.44(1)°, V = 773.5(2) ų, Z = 1). The Cu atoms are fivefold coordinated by two Cl atoms, two N atoms of phen ligands and one O atom of the adipate anion, forming [CuCl₂N₂O] square pyramids with an axial Cl atom (d(Cu–O) = 1.958 Å, d(Cu–N) = 2.017–2.033 Å, d(Cu–Cl) = 2.281 Å; axial d(Cu–Cl) = 2.724 Å). Two square pyramids are condensed via the common Cl–Cl edge to centrosymmetric [Cu₂Cl₂N₄O₂] dimers, which are connected via the adipate anions to form the [(Cu₂(phen)₂Cl₂)(C₆H₈O₄)_2/2] chains. The supramolecular 3 D network results from π‐π stacking interactions between the chains. H₂O molecules are located in tunnels.     

An Azelaato‐bridged Dinuclear Copper(II) Complex, [Cu2(phen)2(C9H14O4)2] · 6 H2O (phen = 1,10‐phenanthroline)

The title compound [Cu₂(phen)₂(C₉H₁₄O₄)₂] · 6 H₂O was prepared by the reaction of CuCl₂ · 2 H₂O, 1,10‐phenanthroline (phen), azelaic acid and Na₂CO₃ in a CH₃OH/H₂O solution. The crystal structure (monoclinic, C2/c (no. 15), a = 22.346(3), b = 11.862(1), c = 17.989(3) Å, β = 91.71(1)°, Z = 4, R = 0.0473, wR² = 0.1344 for 4279 observed reflections) consists of centrosymmetric dinuclear [Cu₂(phen)₂(C₉H₁₄O₄)₂] complexes and hydrogen bonded H₂O molecules. The Cu atom is square‐planar coordinated by the two N atoms of the chelating phen ligand and two O atoms of different bidentate bridging azelaate groups with d(Cu–N) = 2.053, 2.122(2) Å and d(Cu–O) = 1.948(2), 2.031(2) Å. Two azelaate anions bridge two common Cu atoms via the terminal O atoms (d(C–O) = 1.29(2) Å; d(C–C) = 1.550(4)–1.583(4) Å). Phen ligands of adjacent complexes cover each other at distances of about 3.62 Å, indicating π‐π stacking interaction, by which the complexes are linked to 1 D bands.     

Synthesis and Crystal Structure of the Tris‐bidentate Carbonatobis‐(1,10‐phenanthroline‐N,N′)nickel(II), [Ni(C12H8N2)2(CO3)]

The tris‐bidentate complex [Ni(C₁₂H₈N₂)₂(CO₃)] was synthesized by the reaction of Na₂CO₃, 1,10‐phenanthroline (phen = C₁₂H₈N₂) and NiSO₄ · 6 H₂O in the presence of succinic acid in a CH₃OH–H₂O solution. The compound crystallizes as heptahydrate. The crystal structure (monoclinic, P2₁/c (no. 14), a = 9.897(1), b = 26.384(2), c = 10.582(1) Å, β = 105.87(1)°, Z = 4, R = 0.0505, wR² = 0.1029 for 3166 observed reflections (F ≥ 2σ(F ) out of 6100 unique reflections) consists of hydrogen bonded water molecules and [Ni(phen)₂(CO₃)] complex molecules. The Ni atoms are sixfold octahedrally coordinated by the four N atoms of two bidentate chelating phen ligands and by two O atoms of the bidentate chelating carbonate group with d(Ni–N) = 2.092–2.100 Å, d(Ni–O) = 2.051, 2.079 Å. The complex molecules are stacked into 2D corrugated layers parallel to (010) via two types of intermolecular π‐π stacking interactions. One occurs between two quinoline rings of neighboring phen ligands at the distance of 3.63 Å in [010] direction and the other results from 1D π‐π stacking interactions through partially covered phen rings at alternative distances of 3.26 Å and 3.33 Å in [001] direction. The water molecules are sandwiched between 2D layers.     

Construction of Hetero‐Four‐Layered Tripalladium(II) Cyclophanes by Transannular π⋅⋅⋅π Interactions

A synthetic strategy for the generation of new molecular species utilizing a provision of nature is presented. Nano‐dimensional (23(2)×21(1)×16(1) ų) hetero‐four‐layered trimetallacyclophanes were constructed by proof‐of‐concept experiments that utilize a suitable combination of π???π interactions between the central aromatic rings, tailor‐made short/long spacer tridentate donors, and the combined helicity. The behavior of the unprecedented four‐layered metallacyclophane system offers a landmark in the development of new molecular systems.     

Crystal Structures of [Mn2(H2O)4(bpy)2(C8H12O4)2] · 2 H2O and [Mn(H2O)2(bpy)(C8H12O4)2/2] · H2O with bpy = 2,2′‐bipyridine

Reaction of MnSO₄ · H₂O, 2,2′‐bipyridine (bpy), suberic acid and Na₂CO₃ in CH₃OH/H₂O yielded a mixture of [Mn₂(H₂O)₄(bpy)₂(C₈H₁₂O₄)₂] · 2 H₂O ( 1 ) and [Mn(H₂O)₂‐ (bpy)(C₈H₁₂O₄)_2/2] · H₂O ( 2 ). In both complexes, the Mn atoms are octahedrally coordinated by two N atoms of one bpy ligand and four O atoms of two trans positioned H₂O molecules and two suberato ligands (d(Mn–O) = 2.107–2.328 Å; d(Mn–N) = 2.250–2.330 Å). The bis‐monodentate suberato ligands bridge Mn atoms to form dinuclear [Mn₂(H₂O)₄(bpy)₂(C₈H₁₂O₄)₂] complex molecules in 1 and 1D [Mn(H₂O)₂(bpy)(C₈H₁₂O₄)_2/2] chains in 2 . Via the intermolecular hydrogen bondings and π‐π stacking interactions, the dinuclear molecules in 1 are assembled into 2D networks parallel to (100), between which the crystal H₂O molecules are sandwiched. The polymeric chains in 2 are linked together by interchain hydrogen bonding and π‐π stacking interactions into 3D networks with the crystal H₂O molecules located in tunnels along [010]. Crystal data for 1 : P2₁/c (no. 14), a = 10.092(1) Å, b = 11.916(2) Å, c = 17.296(2) Å, β = 93.41(1)° and Z = 2. Crystal data for 2 : P2₁/c (no. 14), a = 11.176(2) Å, b = 9.688(1) Å, c = 37.842(6) Å, β = 90.06(1)° and Z = 8.