Platinum(II) Terpyridyl-Acetylide Dyads and Triads with Nitrophenyl Acceptors via a Convenient Synthesis of a Boronated Phenylterpyridine

Supramolecular assembly of bent dinuclear amphiphilic alkynylplatinum(ii) terpyridine complexes: diverse nanostructures through subtle tuning of the mode of molecular stacking

A new class of bent amphiphilic alkynylplatinum(ii) terpyridine complexes was found to adopt different modes of molecular stacking to give diverse nanostructures.

A new class of bent amphiphilic alkynylplatinum(ii) terpyridine complexes was found to adopt different modes of molecular stacking to give diverse nanostructures. In chlorinated solvents, the complexes aggregate in the presence of water droplets and assist in the formation of porous networks, while in DMSO solutions, they self-assemble to give fibrous nanostructures. The complexes would adopt a head-to-tail tetragonal stacking arrangement, as revealed by X-ray crystallographic studies, computational studies and powder X-ray diffraction (PXRD) studies. Their self-assembly follows a cooperative growth mechanism in DMSO and an isodesmic growth mechanism in DMSO–H₂O mixture. The balance between hydrophobic and hydrophilic components of the complex system, in conjunction with the nuclearity and the positioning of the substituents, are found to govern the mode of molecular stacking and the fabrication of precise functional nanostructures. This class of complexes serve as versatile building blocks to construct orderly packed molecular materials and functional materials in a well-controlled manner.

Supramolecular assembly of a phosphole-based moiety into nanostructures dictated by alkynylplatinum(ii) terpyridine complexes through non-covalent Pt···Pt and π-π stacking interactions: synthesis, characterization, photophysics and self-assembly behaviors

A new class of platinum(ii) terpyridine complexes with a phosphole-derived bridging alkynyl ligand have been prepared. The X-ray crystal structure of complex 2 has been determined, and reveals a polymeric zig-zag chain structure with the existence of π-π stacking interactions. The photophysical properties have also been studied, with 3MLCT/3LLCT phosphorescence exhibited in degassed CH2Cl2; the energy of which is varied by the π-conjugation of the terpyridine ligands. The solvent-induced assembly of complex 1 has been studied. The incorporation of hydrophobic hydrocarbon chains has been shown to play an important role in assisting the formation of self-assembled nanostructures via Pt···Pt, π-π stacking and hydrophobic-hydrophobic interactions. It has been established that an isodesmic growth mechanism operates in polar media to give nanospheres, while fibrous networks originate from the self-assembly of the complexes in non-polar media, predominantly driven by π-π stacking interactions.

Hypochlorite-promoted inhibition of photo-induced electron transfer in phenothiazine–borondipyrromethene donor–acceptor dyad: a cost-effective and metal-free “turn-on” fluorescent chemosensor for hypochlorite

APTZ-BODIPY based fluorescent chemosensor was designed and used for hypochlorite detection.

Self-assembly of alkynylplatinum(II) terpyridine amphiphiles into nanostructures via steric control and metal-metal interactions

A series of mono- and dinuclear alkynylplatinum(II) terpyridine complexes containing the hydrophilic oligo(para-phenylene ethynylene) with two 3,6,9-trioxadec-1-yloxy chains was designed and synthesized. The mononuclear alkynylplatinum(II) terpyridine complex was found to display a very strong tendency toward the formation of supramolecular structures. Interestingly, additional end-capping with another platinum(II) terpyridine moiety of various steric bulk at the terminal alkyne would lead to the formation of nanotubes or helical ribbons. These desirable nanostructures were found to be governed by the steric bulk on the platinum(II) terpyridine moieties, which modulates the directional metal-metal interactions and controls the formation of nanotubes or helical ribbons. Detailed analysis of temperature-dependent UV-visible absorption spectra of the nanostructured tubular aggregates also provided insights into the assembly mechanism and showed the role of metal-metal interactions in the cooperative supramolecular polymerization of the amphiphilic platinum(II) complexes.

Self-assembly of triangular metallomacrocycles using unsymmetrical bisterpyridine ligands: isomer differentiation via TWIM mass spectrometry

Three unsymmetrical, 60°-bended bisterpyridine ligands with varying phenylene spacer lengths have been synthesized via the Suzuki-Miyaura coupling reactions. Their self-assembly processes were found to be strongly dependent on the ligand geometry. Upon complexation with Zn(II) ions, only 2,4''-di(4'-terpyridinyl)-1,1':4',1''-terphenyl underwent self-selection to give a trinuclear metallomacrocycle with perfect heteroleptic connectivity and the other two afforded a mixture of constitutional isomers. The metallosupramolecular assemblies were characterized by NMR spectroscopy, electrospray mass spectrometry (ESI MS), and single-crystal X-ray diffraction. In particular, the identification of isomeric architecture was accomplished using tandem mass spectrometry (MS(2)) coupled with traveling wave ion mobility mass spectrometry (TWIM MS).

Dynamic scaffold of chiral binaphthol derivatives with the alkynylplatinum(II) terpyridine moiety

Platinum(II)-containing complexes with inherently chiral binaphthol derivatives display a versatile scaffold between random coils and single-turn helical strands, in which the conformational transition is controlled by the Pt···Pt and π-π interactions of alkynylplatinum(II) terpyridine moiety upon solvent and temperature modulation. The bisignate Cotton effect in the circular dichroism spectra is indicative of the cooperative transformation from random coil state to a compact single-turn M- or P-helix. More importantly, as revealed by the appearance of new UV-vis absorption and emission bands during conformational change, the self-assembly of the platinum(II)-containing complex into a helical structure is assisted by the metal···metal and π-π interactions of the alkynylplatinum(II) terpyridine moieties. The folded structure with stabilization via metal···metal and π-π interactions has been supported by density functional theory calculations, which provide insights into the folded geometry of these kind of metallo-foldamers.

Self-assembly of luminescent alkynylplatinum(II) terpyridyl complexes: modulation of photophysical properties through aggregation behavior

Complexes of platinum(II) with polypyridine (that is, the multidentate ligands related to pyridine, such as bipyridine or terpyridine) have rich photophysical properties. These compounds are able to give different crystal forms in the solid state: this polymorphism is evident in the broad range of colors that can be observed in solid samples. Because of the square-planar coordination geometry of the metal center, Pt···Pt as well as π-π interactions between the chromophoric polypyridyl platinum(II) moieties are thought to contribute to the polymorphism. Owing to limited solubility, metal···metal interactions in platinum(II) polypyridyl systems had been mainly studied in the solid state, but our preparation of more soluble complexes has enabled detailed spectroscopic examinations in solution. In this Account, we describe our development of these alkynylplatinum(II) terpyridyl complexes and their unique spectral properties. A series of square-planar platinum(II) terpyridyl complexes with enhanced solubility due to the presence of the alkynyl group exhibited intense emission in solution. The lowest energy absorption and emission bands are suggested to originate from the dπ(Pt) → π*(terpy) metal-to-ligand charge transfer (MLCT) and π(C≡C-C(6)H(4)-R) → π*(terpy) ligand-to-ligand charge transfer (LLCT) transitions. In addition to polymorphism and a wide range of spectral properties, these complexes also exhibit "solvatochromism" and "solvatoluminescence". They show remarkable color changes and luminescence enhancement when the diethyl ether content in a solvent mixture is varied, even as the concentration of the platinum(II) complex is held constant. The dramatic color changes and luminescence enhancement are tentatively suggested to originate from a metal-metal-to-ligand charge transfer (MMLCT) transition: reduced solvation (caused by an increase in the fraction of diethyl ether, which is the nonsolvating component of the liquid) is thought to increase Pt···Pt and π-π stacking interactions that arise from ground-state self-assembly or aggregate formation. The absorbance and luminescence wavelengths in these solvent-induced self-assemblies are also found to be dependent on the nature of the anions. Thus, counterions play an important role in governing the degree of self-assembly and the extent of interactions within these aggregates. Several polymers carrying multiple negatively charged functional groups (under basic conditions) as well as oligonucleotides have been shown to induce the aggregation and self-assembly of the positively charged water-soluble alkynylplatinum(II) terpyridyl complexes. The driving force for the induced aggregation and self-assembly is electrostatic binding of the complex molecules to the polymer, which brings the cations into a close proximity that induces Pt···Pt and π-π interactions and gives rise to remarkable color changes and luminescence enhancement. The spectral changes are shown to be related to the properties of both the complexes and the polymers. Upon electrostatic interaction, the platinum(II) complex cations are also found to stabilize the polymers and biopolymers in a helical conformation through Pt···Pt and π-π interactions. The influence on their secondary structure is revealed by significant circular dichroism (CD) signal enhancement.