Integrative assembly of heteroleptic tetrahedra controlled by backbone steric bulk

A bent fluorenone-based dipyridyl ligand LA reacts with PdII cations to a solvent-dependent dynamic library of [PdnL2n] assemblies, constituted by a [Pd3LA6] ring and a [Pd4LA8] tetrahedron as major components, and a [Pd6LA12] octahedron as minor component. Introduction of backbone steric hindrance in ligand LB allows exclusive formation of the [Pd6LB12] octahedron. Combining equimolar amounts of both ligands results in integrative self-sorting to give an unprecedented [Pd4LA4LB4] heteroleptic tetrahedron. Key to the non-statistical assembly outcome is exploiting the structural peculiarity of the [Pd4L8] tetrahedral topology, where the four lean ligands occupy two doubly bridged edges and the bulky ligands span the four remaining, singly bridged edges. Hence, the system finds a compromise between the entropic drive to form an assembly smaller than the octahedron and the enthalpic prohibition of pairing two bulky ligands on the same edge of the triangular ring. The emission of luminescent LA is maintained in both homoleptic [Pd3LA6] and heteroleptic [Pd4LA4LB4]

NO Reduction Cycle on Dinuclear Ruthenium Complexes having Hydrotris(pyrazolyl)borato

ナノダイナミクス国際シンポジウム 平成22年1月21日(木) 於長崎大学Nagasaki Symposium on Nano-Dynamics 2010 (NSND2010), January 21, 2010, Nagasaki University, Nagasaki, Japan, Invited Lectur

Reversible formation and cleavage of Pt→Ag dative bonds in a pre-organized cavity of a luminescent heteropolynuclear platinum(ii) complex

A U-shaped Pt2Ag2 complex [Pt2Ag2(ppy)2(Ph2pz)4] with a pre-organized cavity (ppy = 2-phenylpridinate and Ph2pz = 3,5-diphenylpyrazolate) and related complexes have been prepared. The Pt2Ag2 complexes react with Ag(I) ions to give the corresponding Pt2Ag3 complexes containing Pt→Ag dative bonds. It became obvious that the existence of the C(ipso) atom in the chelate ligand is important as the driving force for forming Pt→Ag dative bonds. However, once the Pt2Ag3 complex is formed, the trapped Ag(I) ion is mainly stabilized by the Pt→Ag dative bonds, which are stronger than the Ag?C(ipso) bond. The trapped Ag(I) ion can be abstracted from the cavity selectively by adding an equivalent amount of chloride ion into the solution of Pt2Ag3 complexes to reproduce the original Pt2Ag2 complexes.Related illustration appears in this issue\u27s inside back cover. The URL is as follows: http://dx.doi.org/10.1039/C7CC90232

Bridging-arylene effects on spectroscopic and photophysical properties of arylborane–dipyrrinato zinc(ii) complexes

Novel bis(dipyrrinato)zinc(ii) derivatives having 4-[bis(2,4,6-trimethylphenyl)boryl]phenyl (ZnBph) or 4-[bis(2,4,6-trimethylphenyl)boryl]-2,3,5,6-tetramethylphenyl groups (ZnBdu) at the 5-position of the dipyrrinato ligands were designed and synthesized.InZnBphwith the smaller dipyrrinate-arylene and arylene-dimesitylboryl dihedral angles, an intramolecular charge transfer arising from the presence of the vacant p orbital on the boron atom participates in the ππ* excited state in character in contrast to the pure ππ* excited state ofZnBdu. The synergistic ππ*/ILCT excited state was weakly fluorescent, and the fluorescence was enhanced upon binding of fluoride to the boron atom

Synthesis and photophysical properties of butterfly-shaped dinuclear Pt(II) complex having NHC-based chelate ligands

A butterfly-shaped dinuclear Pt(II) complex having pyridyl-NHC chelate ligands and bridging Me2pz ligands was synthesized. The crystal structure of the Pt2 complex showed short intramolecular Pt?Pt distance (3.129?A) and unique packing structure containing one-dimensional infinite pore that was filled with solvent molecules. The absorbance was proportional to the concentration of Pt2 complex and no significant bands appeared even in high concentration (up to 100?μM). The Pt2 complex showed bluish-green emission (λmax?=?459?nm) in the solid state at 298?K (λex?=?330?nm). TD-DFT calculation revealed that the lowest-energy absorption bands are mainly assigned to the combination of metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (LLCT) transitions

Symmetry-breaking host–guest assembly in a hydrogen-bonded supramolecular system

Bio-inspired self-assembly is invaluable to create well-defined giant structures from small molecular units. Owing to a large entropy loss in the self-assembly process, highly symmetric structures are typically obtained as thermodynamic products while formation of low symmetric assemblies is still challenging. In this study, we report the symmetry-breaking self-assembly of a defined C1-symmetric supramolecular structure from an Oh-symmetric hydrogen-bonded resorcin[4]arene capsule and C2-symmetric cationic bis-cyclometalated Ir complexes, carrying sterically demanding tertiary butyl (tBu) groups, on the basis of synergistic effects of weak binding forces. The flexible capsule framework shows a large structural change upon guest binding to form a distorted resorcin[4]arene hexameric capsule, providing an asymmetric cavity. Location of the chiral guest inside the anisotropic environment leads to modulation of its Electric Dipole (ED) and Magnetic Dipole (MD) transition moments in the excited state, causing an increased emission quantum yield, longer emission lifetime, and enhancement of the dissymmetry factor (glum) in the circularly polarized luminescence

Methylation of a nitrosylruthenium complex bearing a hydridotris(pyrazolyl)borate ligand

Reaction of [TpRuCl2(NO)] (1) (Tp = HB(pyrazol-1-yl) 3) with dimethylzinc, Zn(Me)2, gave rise to a dimethyl complex [TpRu(Me)2(NO)] (2) and a monomethyl complex [TpRuCl(Me)(NO)] (3) in good yields, while the use of a Grignard reagent, MeMgCl, as the alkylating agents led to isolation of 2 in low yield. Complexes 2 and 3 were confirmed by single-crystal X-ray diffraction analyses. Treatment of 2 with triflic acid, CF3SO3H, afforded a triflato complex [TpRu(Me){OS(O)2CF3}(NO)] (4)

Encapsulation condition dependent photophysical properties of polypyridyl Ru(ii) complexes within a hydrogen-bonded capsule

Controlling the encapsulation equilibrium is a key strategy to affect host-guest associations. Ruthenium(ii) polypyridyl complex salts suspended in a chloroform solution of resorcin[4]arene afforded a host-guest complex which showed structured emission spectra even in the solution state. In contrast, a host-guest complex obtained through homogeneous encapsulation conditions by using soluble ruthenium(ii) polypyridyl complex salts showed broadened emission spectra which strongly depended on the amount of the host owing to the encapsulation equilibrium. These results demonstrate that a simple modulation of the encapsulation technique is indeed promising and a facile approach to control the photophysical properties of supramolecular complexes

Reactions of (polypyrazolylborato)(benzonitrile)rutheniums with terminal alkynes: Reactivity changeover by triethylamine toward arylalkyne polymerization or formation of (arylmethyl)(carbonyl) complexes

Reactions of (κ 3-polypyrazolylborato)(benzonitrile) rutheniums [RuCl{B(4-Ypz) 4}(PhCN) 2] {4-Ypz; 4-bromo-1-pyrazolyl (Y = Br) and 1-pyrazolyl (Y = H) groups} with terminal alkynes were studied. For the reactions with arylalkynes HC≡C(aryl) in the presence of NEt 3, (arylmethyl)(carbonyl)rutheniums [Ru{CH 2(aryl)}{B(4-Ypz) 4}(CO)(PhCN)] were yielded, indicating alkyne C≡C bond cleavage, whereas in the absence of NEt 3, arylalkyne polymerization proceeded instead of the (arylmethyl)ruthenium formation. Reasonably attributed reaction mechanism shows significant role of the vinylidene intermediates "Ru=C=CH(aryl)"