Hongwei Tan

Vapochromic Behavior of a Chair-Shaped Supramolecular Metallacycle with Ultra-Stability

A new discrete supramolecular metallacycle functionalized with an alkynylplatinum(II) bzimpy moiety was successfully prepared via coordination-driven self-assembly, and it displayed a reversible color change in the solid state between yellow and red, triggered by CH2Cl2 vapor or mechanical grinding. Notably, unlike many known vapochromic systems, the obtained vapochromic metallacycle exhibits ultra-stability, with the red color remaining unchanged in air for several months at room temperature or even under vacuum for >1 week. Further investigation revealed that the chair conformation of the metallacyclic scaffold, which was thought to prevent intermolecular steric repulsion between the alkyl chain and triethylphosphine, favored close molecular stacking through intermolecular Pt···Pt and π-π stacking interactions, thus allowing such vapochromic behavior with ultra-stability.

Design and Construction of Endo-Functionalized Multiferrocenyl Hexagons via Coordination-Driven Self-Assembly and Their Electrochemistry

The construction of a new family of endo-functionalized multiferrocenyl hexagons with various sizes via coordination-driven self-assembly is described. The structures of these novel metallacycles, containing several ferrocenyl moieties at their interior surface, are characterized by multinuclear NMR ((31)P and (1)H) spectroscopy, cold-spray ionization mass spectrometry (CSI-TOF-MS), elemental analysis, and molecular modeling. Insight into the structural and electrochemical properties of these endo-functionalized multiferrocenyl hexagons was obtained through cyclic voltammetry investigation.

Design and Synthesis of 60° Dendritic Donor Ligands and Their Coordination-Driven Self-Assembly into Supramolecular Rhomboidal Metallodendrimers

The design and self-assembly of novel rhomboidal metallodendrimers via coordination-driven self-assembly is described. By employing newly designed 60° ditopic donor linkers substituted with Fréchet-type dendrons and appropriate 120° rigid di-Pt(II) acceptor subunits, a variety of [G-1]-[G-3] rhomboidal metallodendrimers with well-defined shape and size were prepared under mild conditions in high yields. The supramolecular metallodendrimers were characterized with multinuclear NMR ((1)H and (31)P), mass spectrometry (CSI-TOF-MS), and elemental analysis. Isotopically resolved mass spectrometry data support the existence of the metallodendrimers with rhomboidal cavities, and NMR data were consistent with the formation of all ensembles. The shape and size of all rhomboidal metallodendrimers were investigated with the PM6 semiempirical molecular orbital method.

Coordination-Driven Self-Assembly of Carbazole-Based Metallodendrimers with Generation-Dependent Aggregation-Induced Emission Behavior

A new family of 120° carbazole-based dendritic donors D1-D3 have been successfully designed and synthesized, from which a series of novel supramolecular carbazole-based metallodendrimers with well-defined shapes and sizes were successfully prepared by [2+2] and [3+3] coordination-driven self-assembly. The structures of newly designed rhomboidal and hexagonal metallodendrimers were characterized by multinuclear NMR ((1) H and (31) P) spectroscopy, ESI-TOF mass spectrometry, FTIR spectroscopy, and the PM6 semiempirical molecular orbital method. The fluorescence emission behavior of ligands D1-D3, rhomboidal metallodendrimers R1-R3, and hexagonal metallodendrimers H1-H3 in mixtures of dichloromethane and n-hexane with different n-hexane fractions were investigated. The results indicated that D1-D3 featured typical aggregation-induced emission (AIE) properties. However, different from ligands D1-D3, metallodendrimers R1-R3 and H1-H3 presented interesting generation-dependent AIE properties. Furthermore, evidence for the aggregation of these metallodendrimers was confirmed by a detailed investigation of dynamic light-scattering, Tyndall effect, and SEM. This research not only provides a highly efficient strategy for constructing carbazole-based dendrimers with well-defined shapes and sizes, but also presents a new family of carbazole-based dendritic ligands and rhomboidal and hexagonal metallodendrimers with interesting AIE properties.

Branched platinum–acetylide complexes: synthesis, properties, and their aggregation behavior

A new branched platinum–acetylide complex PP6 containing pyrene as the main skeleton, pentiptycene units as bridges, and long alkyl chains as branches was successfully synthesized. The structure of PP6 was well characterized by 1H NMR, 31P {1H} NMR, MALDI-TOF-MS spectrometry, and the semiempirical PM6 method. The investigation of the absorption and emission spectra of PP6 and the model complexes revealed that the introduction of iptycene was beneficial to improve the emission efficiency. More importantly, PP6 was aggregated into ordered microspheres driven by the hydrophobic/hydrophilic interactions. The morphologies of the microspheres were investigated by SEM, TEM, LSCM, and EDX. Furthermore, the morphologies and the sizes of the microscale aggregates could be changed by altering the iptycene moiety or the hydrophobic units in PP6.

A single chemosensor for bimetal Cu(II) and Zn(II) in aqueous medium

A new quinazoline derivative 6-(4-diethylamino)phenol-2-yl-(5,6-dihydrobenzimidazo[1,2-c])-quinazoline (HL) and the two metal Schiff-base complexes [CuL1Cl]·CH3OH (1) and [ZnL1(Ac)]·0.5CH3CH(OH)CH3 (2) (HL1 = 4-{[2-(1H-benzoimidazol-2-yl)-phenyl imino]-methyl}-benzene-1-diethylamino-3-ol) were synthesized and characterized by single-crystal X-ray diffraction. HL is highly selective and sensitive to Cu(II) and Zn(II) ions in aqueous medium with a detection limit of 2.13 × 10−6 and 7.19 × 10−7 M for Cu2+ and Zn2+, respectively. HL can act as a “turn-off” sensor for Cu(II) with the excitation wavelength of 356 nm and a “turn-on” sensor for Zn(II) when excited at 416 nm. The Job plots, fluorescence and UV-vis titrations, 1H NMR as well as ESI data show that the binding stoichiometry of Cu(II)/Zn(II) with HL is 1 : 1. The binding sites of HL with Cu(II)/Zn(II) are two nitrogen atoms and one oxygen atom, forming Cu(II)–L1 and Zn(II)–L1 complexes. This agrees with the crystal structures of 1 and 2.

Peripherally diketopyrrolopyrrole-functionalized dendritic oligothiophenes – synthesis, molecular structure, properties and applications

Three-dimensional π-conjugated dendrimers are a class of structure defined macromolecules for use in organic electronics. Herein, a new family of dendritic oligothiophenes (DOT-p-DPPs) that are functionalized with the diketopyrrolopyrrole group at the periphery were synthesized by a precise stepwise approach. The chemical structure and the monodisperse nature of these DOT-p-DPPs were confirmed by NMR, MALDI-TOF MS, HR MS, and GPC measurements. UV-vis absorption and fluorescence spectra and cyclic voltammetry data of these compounds were also measured. Small band gaps (∼1.8 eV) and almost identical HOMO/LUMO energy levels (−5.2/−3.5 eV) were measured for these DOT-p-DPPs independent of the molecular size. However, the molecular molar extinction coefficient (e) of DOT-p-DPPs was found to be linearly correlated with the number of terminal DPP units, and a high e of 3.6 × 105 cm−1 L mol−1 was measured for the bigger molecules. These results in combination with theoretical calculation results confirm that the frontier molecular orbitals are mostly localized over the peripheral DPP units. The applications of DOT-p-DPPs in organic solar cells as the electron donor are presented. However, unfavorable nanophase separation and lower DOT-p-DPP content in the blended films led to poor device performance. The two photon absorption cross section of these DPP decorated dendrimers was measured, and high cross section values of over 2000 GM were measured for these dendritic molecules, among which the G1 dendrimer 6T-p-DPP with a high TPA cross section value close to 7000 GM was achieved.

Dual stimuli-responsive rotaxane-branched dendrimers with reversible dimension modulation

With the aim of mimicking biological machines, in which the delicate arrangement of nanomechanical units lead to the output of specific functions upon the external stimulus, the construction of dual stimuli-responsive rotaxane-branched dendrimers was realized in this study. Starting from a switchable organometallic [2]rotaxane precursor, the employment of a controllable divergent approach allowed for the successful synthesis of a family of rotaxane-branched dendrimers up to the third generation with 21 switchable rotaxane moieties located on each branch. More importantly, upon the addition and removal of dimethylsulfoxide (DMSO) molecule or acetate anion as the external stimulus, the amplified responsiveness of the switchable rotaxane units endowed the resultant rotaxane-branched dendrimers the solvent- or anion-controlled molecular motions, thus leading to the dimension modulation. Therefore, we successfully constructed a family of rotaxane-branched dendrimers with dual stimuli-responsiveness that will be a privileged platform for the construction of dynamic supramolecular materials.Mechanically interlocked molecules are extensively applied as artificial molecular machines but rotaxane-branched dendrimers are rarely explored because of synthetic challenges. Here the authors present the construction of dual stimuli-responsive rotaxane-branched dendrimer which can be stimulated by DMSO or acetate ions.