Selective adsorption behaviors of guest molecules COR in the hexamer host networks at liquid/solid interface

Here,the selective adsorption behaviors of guest molecule COR in two hexamer host grids were investigated by means of scanning tunnelling microscope(STM).The assembled structures of small functional organic molecules TTBTA and TATBA were thermodynamically stable.Interestingly,the introduction of the guest molecule COR destroyed the original hexamer structure of TTBTA and combined with it to form a new triangular host-guest system.Different from TTBTA,the introduction of the guest molecule COR did not affect the six-membered ring structure of TATBA.Furthermore,the co-assembly structure of TTBTA/TATBA/COR was established and the guest molecule COR showed preferential adsorption to the TATBA host grid.Density functional theory(DFT) calculations had been performed to disclose the mechanism of the involved assemblies.     

Reporters in the nanoworld: diffusion of single molecules in mesoporous materials

Mesoporous materials have a high potential for a number of different applications in Materials Science such as in molecular sieving, as masks for the formation of nanometre-sized metallic wires, as novel drug-delivery systems or as advanced host systems for catalysis. For many of these applications a thorough understanding of the interaction of guest molecules within the host matrix is required. In this tutorial review, we cover recent single-molecule experiments that allow the investigation of host-guest dynamics with unprecedented detail. We will show how molecules diffusing in samples with (almost) perfect domain ordering still show a large heterogeneity in their mobility and interaction with the host. With the presented methodology it is now possible to dramatically improve our understanding of host-guest interactions and in return develop new nano-structured mesoporous materials with properties optimised for a certain application.     

Hydrogen-bonded metal-complex sulfonate (MCS) inclusion compounds: effect of the guest molecule on the host framework

Soft molecular host frameworks made of the hydrogen-bonded metal complex (MC) Co(NH3)(6)3+ and 4,4'-biphenyldisulfonate (BPDS) include different guest molecules to form inclusion compounds of the type (MC)2(BPDS)3.n(guest). Structurally characterized were six compounds with guest molecules of DMSO, DMF, piperidine, acetone, acetonitrile, and THF. The metal-complex sulfonate frameworks in all of them are of the pillared layer type where the layers are constructed of extensively hydrogen-bonded metal-complex cations and sulfonate (S) anions (and some hydrogen-bonded water) while the organic residues of the 4,4'-biphenyldisulfonate serve as pillars. The hydrogen-bonded MCS layers and the orientations of the pillars adjust and rearrange in order to generate cavities that would accommodate different guest molecules. The steric, electronic, and hydrogen-bonding needs of the guest molecules mold the soft framework into different structures. These MCS host-guest frameworks are very close structural analogues of the well-studied guanidinium sulfonate (GS) networks and mimic their flexibility and overall durability.     

Equilibrium isotope effects on noncovalent interactions in a supramolecular host-guest system

The self-assembled supramolecular complex [Ga(4)L(6)](12-) (1; L = 1,5-bis[2,3-dihydroxybenzamido]naphthalene) can act as a molecular host in aqueous solution and bind cationic guest molecules to its highly charged exterior surface or within its hydrophobic interior cavity. The distinct internal cavity of host 1 modifies the physical properties and reactivity of bound guest molecules and can be used to catalyze a variety of chemical transformations. Noncovalent host-guest interactions in large part control guest binding, molecular recognition and the chemical reactivity of bound guests. Herein we examine equilibrium isotope effects (EIEs) on both exterior and interior guest binding to host 1 and use these effects to probe the details of noncovalent host-guest interactions. For both interior and exterior binding of a benzylphosphonium guest in aqueous solution, protiated guests are found to bind more strongly to host 1 (K(H)/K(D) > 1) and the preferred association of protiated guests is driven by enthalpy and opposed by entropy. Deuteration of guest methyl and benzyl C-H bonds results in a larger EIE than deuteration of guest aromatic C-H bonds. The observed EIEs can be well explained by considering changes in guest vibrational force constants and zero-point energies. DFT calculations further confirm the origins of these EIEs and suggest that changes in low-frequency guest C-H/D vibrational motions (bends, wags, etc.) are primarily responsible for the observed EIEs.     

Macrocyclic versus acyclic preorganization in organoplatinum(II)-based host-guest complexes

Two host-guest systems have been constructed,by employing structurally similar terpyridine platinum (II) macrocycle and molecular tweezer as the synthetic receptors.The macrocycle/guest complex displays low-energy emission signal,reinforced non-covalent binding affinity,and enhanced photosensitization capability than those of the molecular tweezer/guest one.The discrepancy between macrocyclic and acyclic preorganization modes originates from the different numbers of Pt (II)...Pt (II) metal-metal bonds in host-guest complexation structures.     

微孔化合物生成中的结构导向与模板作用

本文详细总结了各种客体分子或离子在无机微孔化合物生成中的结构导向与模板作用。讨论了不同合成体系中,客体与无机骨架间的非键相互作用对生成骨架结构的影响以及分子模拟在研究主-客体关系、结构导向剂设计与筛选等方面的进展。无机或有机客体与无机骨架间关系规律的研究,有助于进一步理解结构导向剂(3ＤＡ)作用的机理和微孔化合物的晶化与生成机制,对特定结构微孔化合物的定向合成具有一定的意义。     

环双(对-蒽基-对草快)的分子识别与谱学性质

环双(对-蒽基-对草快)是一种新型的缺电子大环仿生主体, 分子识别是其最重要的应用之一. 考察主体对一系列客体分子如水、氨、醇及杂环等的识别能力, 用密度泛函理论(DFT)中的B3LYP/3-21G基组对主客体复合物的结构进行优化. 在B3LYP/6-31G(d)水平上进行单点能计算, 校正后得到复合物的结合能. 用B3LYP/3-21G方法计算13C和3He化学位移. 结果表明, 主体对客体分子的识别主要靠客体上的杂原子与主体上的氢原子之间的氢键进行. 复合物的稳定化能受氢键的数目和距离影响. 氢键的形成导致部分复合物LUMO与HOMO能隙增大, 同时导致与氢键相连的C—H键上C原子的化学位移向低场移动. 复合物的芳香性与其结合能的大小及结合方式有关. 主体的芳香性因其与客体之间的弱相互作用而提高, 但太强的相互作用及客体在主体空腔内都将影响主体的环电流, 从而削弱其芳香性.     

Selenium containing macrocycles:transformation between Se-N/Se-S/Se-Se bonds

Macrocycles possess potential applications in supramolecular chemistry and biosystems.Thus development of new kinds of macrocycles is of significance.Herein,novel macrocycles containing Se-Se/Se-S bonds were synthesized via transformation between selenium related dynamic covalent bonds.A monomer containing two ebselen moieties was synthesized(M1).The Se-N bonds in M1 were reduced by dithiothreitol,forming Se-S linked dimer(D1).To realize the transformation from Se-S bonds to Se-Se bonds,guest molecules were added as template,triggering the formation of Se-Se linked dimer(D2).The formation of these two new kinds of macrocycles was determined by ~1H NMR and ~(77)Se NMR,and the necessity of guest molecules was also confirmed.The introduction of ebselen moieties and Se-S bonds or Se-Se bonds into macrocycles may endow it with new responsiveness and bioactivities,as well as new types of host-guest chemistry.     

Recent advance in porous coordination polymers from the viewpoint of crystalline-state transformation

Recently,research of crystalline-state transformation involving the removal/inclusion of guest molecules in porous coordination polymers(PCPs) was underway.Crystalline-state transformation,especially,single-crystal to single-crystal(SC-SC) transformation as new method for the direct observation of host-guest chemistry,can reveal the intrinsic relevance and interaction between the framework and guest molecules.This review describes our work concerning PCPs and recent investigations of others,within the last ...     

Macrocyclic versus acyclic preorganization in organoplatinum(Ⅱ)-based host-guest complexes

Two host-guest systems have been constructed,by employing structurally similar terpyridine platinum(Ⅱ) macrocycle and molecular tweezer as the synthetic receptors.The macrocycle/guest complex displays low-energy emission signal,reinforced non-covalent binding affinity,and enhanced photosensitization capability than those of the molecular tweezer/guest one.The discrepancy between macrocyclic and acyclic preorganization modes originates from the different numbers of Pt(Ⅱ)…Pt(Ⅱ) metal-metal bonds in host-guest complexation structures.     

Molecular recognition: comparative study of a tunable host-guest system by using a fluorescent model system and collision-induced dissociation mass spectrometry on dendrimers

Host-guest interactions between the periphery of adamantylurea-functionalized dendrimers (host) and ureido acetic acid derivatives (guest) were shown to be specific, strong and spatially well-defined. The binding becomes stronger when using phosphonic or sulfonic acid derivatives. In the present work we have quantified the binding constants for the host-guest interactions between two different host motifs and six different guest molecules. The host molecules, which resemble the periphery of a poly(propylene imine) dendrimer, have been fitted with an anthracene-based fluorescent probe. The two host motifs differ in terms of the length of the spacer between a tertiary amine and two ureido functionalities. The guest molecules all contain an acidic moiety (either a carboxylic acid, a phosphonic acid, or a sulfonic acid) and three of them also contain an ureido moiety capable of forming multiple hydrogen bonds to the hosts. The binding constants for all 12 host-guest complexes have been determined by using fluorescence titrations by monitoring the increase in fluorescence of the host upon protonation by the addition of the guest. The binding constants could be tuned by changing the design of the acidic part of the guest. The formation of hydrogen bonds gives, in all cases, higher association constants, demonstrating that the host is more than a proton sensor. The host with the longer spacer (propyl) shows higher association constants than the host with the shorter spacer (ethyl). The gain in association constants are higher when the urea function is added to the guests for the host with the longer spacer, indicating a better fit. Collision-induced dissociation mass spectrometry (CID-MS) is used to study the stability of the six motifs using the corresponding third generation dendrimer. A similar trend is found when the six different guests are compared.     

Controllable macrocyclic supramolecular assemblies in aqueous solution

A series of macrocycles, including crown ethers, cyclodextrins, calixarenes, pillararenes and cucurbiturils, are well known to be able to associate various organic/inorganic/biological guest molecules and ions in their well-defined cyclic cavities to form stable host-guest complexes and supramolecular systems through the cooperative contributions of various non-covalent interactions. When one or more functional groups are attached to the cavity of macrocycles or guest molecules, enhanced and/or controlled host-guest associations may take place, leading to not only improved host-guest binding abilities but also fascinating properties. In this review, some representative contributions in the construction of controllable macrocyclic supramolecular assemblies in aqueous solution are presented with an emphasis on the stimuli-responsive control manner and wide applications of this property.     

Improving the balance of carrier mobilities of host-guest solid-state light-emitting electrochemical cells

We report efficient host-guest solid-state light-emitting electrochemical cells (LECs) utilizing a cationic terfluorene derivative as the host and a red-emitting cationic transition metal complex as the guest. Carrier trapping induced by the energy offset in the lowest unoccupied molecular orbital (LUMO) levels between the host and the guest impedes electron transport in the host-guest films and thus improves the balance of carrier mobilities of the host films intrinsically exhibiting electron preferred transporting characteristics. Photoluminescence measurements show efficient energy transfer in this host-guest system and thus ensure predominant guest emission at low guest concentrations, rendering significantly reduced self-quenching of guest molecules. EL measurements show that the peak EQE (power efficiency) of the host-guest LECs reaches 3.62% (7.36 lm W(-1)), which approaches the upper limit that one would expect from the photoluminescence quantum yield of the emissive layer (～0.2) and an optical out-coupling efficiency of ～20% and consequently indicates superior balance of carrier mobilities in such a host-guest emissive layer. These results are among the highest reported for red-emitting LECs and thus confirm that in addition to reducing self-quenching of guest molecules, the strategy of utilizing a carrier transporting host doped with a proper carrier trapping guest would improve balance of carrier mobilities in the host-guest emissive layer, offering an effective approach for optimizing device efficiencies of LECs.     

Shape‐Persistent Two‐Component 2 D Networks with Atomic‐Size Tunability

Over the past few years, two‐dimensional (2D) nanoporous networks have attracted great interest as templates for the precise localization and confinement of guest building blocks, such as functional molecules or clusters on the solid surfaces. Herein, a series of two‐component molecular networks with a 3‐fold symmetry are constructed on graphite using a truxenone derivative and trimesic acid homologues with carboxylic‐acid‐terminated alkyl chains. The hydrogen‐bonding partner‐recognition‐induced 2D crystallization of alkyl chains makes the flexible alkyl chains act as rigid spacers in the networks to continuously tune the pore size with an accuracy of one carbon atom per step. The two‐component networks were found to accommodate and regulate the distribution and aggregation of guest molecules, such as COR and CuPc. This procedure provides a new pathway for the design and fabrication of molecular nanostructures on solid surfaces.     

Ultralong organic room-temperature phosphorescence of electron-donating and commercially available host and guest molecules through efficient F?rster resonance energy transfer

Ultralong organic room-temperature phosphorescence(RTP) materials have attracted tremendous attention recently due to their diverse applications. Several ultralong organic RTP materials mimicking the host-guest architecture of inorganic systems have been exploited successfully. However, complicated synthesis and high expenditure are still inevitable in these studies. Herein, we develop a series of novel host-guest organic phosphorescence systems, in which all luminophores are electron-rich, commercially available and halogen-atom-free. The maximum phosphorescence efficiency and the longest lifetime could reach 23.6% and 362 ms, respectively. Experimental results and theoretical calculation indicate that the host molecules not only play a vital role in providing a rigid environment to suppress non-radiative decay of the guest, but also show a synergistic effect to the guest through F?rster resonance energy transfer(FRET). The commercial availability, facile preparation and unique properties also make these new host-guest materials an excellent candidate for the anti-counterfeiting application. This work will inspire researchers to develop new RTP systems with different wavelengths from commercially available luminophores.     

Distinct host-guest interaction and subdued fluorescence in a coordination network of 2,3,6,7,10,11-hexakis(phenylthio)triphenylene and silver(I) triflate

This paper reports our recent efforts in using host-guest interactions to control the fluorescent properties of coordination networks containing polycyclic aromatic units. The polycyclic aromatic ligand 2,3,6,7,10,11-hexakis(phenylthio)triphenylene (HPhTT) coordinates with AgTf (Tf: trifluoromethanesulfonate) in nitrobenzene to form single crystals of a 2-D host network consisting of octameric (i.e., containing eight AgTf units) and dimeric AgTf moieties linked to the HPhTT molecules through the Ag-thioether coordination bonds. The HPhTT adopts a starburst and rather irregular conformation, which apparently contributes to the formation of empty space between the 2-D coordination networks. Such voids are occupied by the nitrobenzene guest molecules, resulting in distinct aromatic-aromatic stacking interactions with the triphenylene units (interplanar distances: 3.46 and 3.60 Å). In comparison to a previous Ag-HPhTT network with toluene as weaker-interacting guests, the current system shows a significantly suppressed fluorescent emission from the triphenylene core, apparently due to the quenching effect from the nitrobenzene guests.     

The Preparation of a Water-Soluble Phospholate-Based Macrocycle for Constructing Artificial Light-Harvesting Systems

On the basis of cyclotrixylohydroquinoylene ( CTX ), a novel water-soluble phospholate-based CTX derivative ( WPCTX ) was prepared with facile synthetic procedure and satisfying yield. Several model guest molecules were selected to investigate WPCTX ′s host-guest properties. Based on the study of the host and model guest complexation, a tetraphenylethylene derivative from model guest was employed as a guest molecule ( G ) to form WPCTX⊃G nanoparticles (NPs) with WPCTX through further supramolecular self-assembly in water. Moreover, a hydrophobic fluorescent dye, Eosin Y( ESY ) or Nile red ( NiR ), was encapsulated in WPCTX⊃G NPs to construct two types of artificial light-harvesting systems. Their high antenna effect demonstrated such NPs successfully mimicked light-harvesting systems in nature.     

Host-guest supramolecular chemistry at solid-liquid interface: An important strategy for preparing two-dimensional functional nanostructures

Supramolecular self-assembly,an important strategy in nanotechnology,has been widely studied in the past two decades.In this review,we have introduced the recent progress on construction of two-dimensional(2D)nanostructures by host-guest supramolecular chemistry at solid-liquid interface,and the interactions between the host assembly and the guest molecules are the major concerns.At first,the hydrogen bonds connected hybrid structures are discussed.And then we have paid a close attention on the surface-confined condensation reactions that has flourished recently in direct preparing novel nanostructures with increasing structural complexity.In the end,the cavity confinement of the 2D supramolecular host-guest architectures has been studied.On the basis of the above-mentioned interactions,a group of functional hybrid structures have been prepared.Notably,scanning tunneling microscopy(STM),a unique technique to probe the surface morphology and information at the single molecule level,has been used to probe the formed structures on highly oriented pyrolytic graphite(HOPG)surface.     

Synthesis and Guest-Binding Properties of pH/Reduction Dual-Responsive Cyclophane Dimer

A water-soluble cyclophane dimer having two disulfide groups as a reduction-responsive cleavable bond as well as several acidic and basic functional groups as a pH-responsive ionizable group 1 was successfully synthesized. It was found that 1 showed pH-dependent guest-binding behavior. That is, 1 strongly bound an anionic guest, 6-p-toluidinonaphthalene-2-sulfonate (TNS) with binding constant (K/M⁻¹) for 1:1 host-guest complexes of 9.6 × 10⁴ M⁻¹ at pH 3.8, which was larger than those at pH 7.4 and 10.7 (6.0 × 10⁴ and 2.4 × 10⁴ M⁻¹, respectively), indicating a favorable electrostatic interaction between anionic guest and net cationic 1. What is more, release of the entrapped guest molecules by 1 was easily controlled by pH stimulus. Large favorable enthalpies (ΔH) for formation of host-guest complexes were obtained under the pH conditions employed, suggesting that electrostatic interaction between anionic TNS and 1 was the most important driving force for host-guest complexation. Such contributions of ΔH for formation of host-guest complexes decreased along with increased pH values from acidic to basic solutions. Upon addition of dithiothreitol (DTT) as a reducing reagent to an aqueous PBS buffer (pH 7.4) containing 1 and TNS, the fluorescence intensity originating from the bound guest molecules decreased gradually. A treatment of 1 with DTT gave 2, having less guest-binding affinity by the cleavage of disulfide bonds of 1. Consequently, almost all entrapped guest molecules by 1 were released from the host. Moreover, such reduction-responsive cleavage of 1 and release of bound guest molecules was performed more rapidly in aqueous buffer at pH 10.7.