Toward the Rational Design of Supramolecular Coordination Polymers. The Effect of Solvent and Substituent Changes on the Structure of Self-Assembled Metal-Organometallic Networks

The Effect of Solvent and Coordination Environment of Metal Source on the Self-Assembly Pathway of a Pd(II)-Mediated Coordination Capsule

The effect of reaction environment on the self-assembly process of an octahedron-shaped Pd₆L₈ capsule was investigated. Quantitative analysis of self-assembly process with ¹H NMR spectroscopy revealed that the self-assembly pathway of the capsule was altered by solvent and a leaving ligand coordinating to the metal source, which are not the components of the final self-assembly. Solvents definitively determine the pathway of the self-assembly at a very early stage of the self-assembly. Contrary to the expectation that the weaker the coordination ability of the leaving ligand is, the faster the formation of the final assembly becomes, a leaving ligand with weak coordination ability tends to generate a kinetically trapped species to prevent the capsule formation under mild conditions.

Anion- and Solvent-Induced Assembly and Reversible Structural Transformation of d(10)-Metal Coordination Architectures Containing N-(4-(4-Aminophenyloxy)phenyl)isonicotinamide

We set out studies on anion- and solvent-induced assembly based on the ligand N-(4-(4-aminophenyloxy)phenyl)isonicotinamide (papoa), which is synthesized to show a bent and flexible backbone. Reactions of papoa with ZnX2 (X=Cl, Br, and I) gave the dinuclear macrocycles ([ZnX2 (papoa)]2 ; X=Cl (1 a), Br (2 a), I (3)), the structure of which was determined by X-ray diffraction. Notably, the less bulky Cl and Br compounds afforded the coordinated imine in acetone (i.e., [ZnX2 (papoi)]2 , papoi=N-(4-(4-(propan-2-ylideneamino)phenoxy)phenyl)isonicotinamide; X=Cl (1 b), Br (2 b)), whereas the iodine one only gave the coordinated amine compound 3 under the same reaction condition. In fact, the coordinated imine can return to the amine analogue upon exposure to air or in DMSO, which has been monitored by (1)H NMR spectroscopy and powder X-ray diffraction. Both the dinuclear [Zn(papoa)(NO3)2]2 (4 a) and the 1D [Zn(papoa)2(NO3)2]n (4 b) were formed from the reaction of Zn(NO3)2 and papoa in mixed solvents with acetone and acetonitrile, respectively. In addition, Cd(ClO4)2 can react with papoa to give the 1D framework {[Cd(papoa)2 (CH3CN)2](ClO4)2}n (5 a) and the 2D framework [Cd(papoa)2 (ClO4)2]n (5 b), depending on the solvent used, that is, MeOH and CH3CN, respectively. Importantly, the 1D framework with axially coordinated CH3 CN molecules and the 2D framework with axially coordinated ClO4(-) ions can be interconverted by heating and grinding in the presence of CH3CN, respectively. Such a reversible structural transformation process was proven by PXRD studies.

π-Bonded quinonoid transition-metal complexes

Coordination of the carbocyclic ring of hydroquinones to electrophilic transition-metal fragments such as Mn(CO)3+ and Rh(COD)+ produces stable pi-bonded eta6-complexes that are activated to facile reversible deprotonation of the -OH groups. The deprotonations are accompanied by electron transfer to the transition metal, which acts as an internal oxidizing agent or electron sink. With manganese as the metal, the resulting eta5-semiquinone and eta4-quinone complexes have been used to synthesize one- two- and three-dimensional polymeric metal-organometallic coordination networks. With rhodium as the metal, the pi-quinonoid complexes have been demonstrated to play a unique role in multifunctional C-C coupling catalysis and in the synthesis of new organolithium reagents. Both classes of pi-quinonoid complexes appear to have significant applications in nanochemistry by providing an excellent vehicle for templating the directed self-assembly of nanoparticles into functional materials.

Novel organometallic building blocks for molecular crystal engineering. Part 4. Synthesis and characterization of mono- and bis-amido derivatives of [CoIII(η5-C5H4COOH)2]+ and their utilization as ligands

The synthesis and structural characterization of the hexafluorophosphate salts of the substituted bis-amido molecular complexes [Co(III)(eta5-C5H4CONHC4H3N2)2]+ (1), [Co(III)(eta5-C5H4CONHCH2C5H4N)2]+ (2), [Co(III)(eta5-C5H4CON(C5H4N)2)2]+ (3), and of the amido-carboxyl complexes [Co(III)(eta5-C5H4CON(C5H4N)2)(eta5-C5H4COOH)]+ (4), and [Co(III)(eta5-C5H4CONHC2N3(C5H4N)2)(eta5-C5H4COOH)]+ (5) are reported. The pyridyl and pyrazine substituted amido ligands on the sandwich cores have been chosen because they allow both coordination to metal centres and participation in hydrogen bonding. The hydrogen bonding interactions established by the family of complexes in the solid state has been investigated. The utilization of complex 5 for the preparation of the complex of complexes[Cd(NO3)2{Co(III)(eta5-C5H4CONHC2N3(C5H4N)(C5H4NH))(eta5-C5H4COOH)}2]6+ (6) is reported as a first example of the potential of the substituted mono-and bis-amides as ligands. The isolation and structural characterization of the carbonyl chloride cation [Co(III)(eta5-C5H4COCl)2]+ (7) as its tetrachloro cobaltate anion salt is also described.

An adamantane-based coordination framework with the first observation of discrete metal sulfonate clusters

By employing a rigid adamantane-based unit as a spacer, a coordination solid with an open channel layered structure results showing the first observation of metal sulfonate clusters. The design approach employed enforces a structural mismatch of metal and ligand coordinative preferences.