Multiaddressable molecular rectangles with reversible host-guest interactions: modulation of pH-controlled guest release and capture.

A series of multiaddressable platinum(II) molecular rectangles with different rigidities and cavity sizes has been synthesized by endcapping the U-shaped diplatinum(II) terpyridine moiety with various bis-alkynyl ligands. The studies of the host-guest association with various square planar platinum(II), palladium(II), and gold(III) complexes and the related low-dimensional gold(I) complexes, most of which are potential anticancer therapeutics, have been performed. Excellent guest confinement and selectivity of the rectangular architecture have been shown. Introduction of pH-responsive functionalities to the ligand backbone generates multifunctional molecular rectangles that exhibit reversible guest release and capture on the addition of acids and bases, indicating their potential in controlled therapeutics delivery on pH modulation. The reversible host-guest interactions are found to be strongly perturbed by metal-metal and π-π interactions and to a certain extent, electrostatic interactions, giving rise to various spectroscopic changes depending on the nature of the guest molecules. Their binding mode and thermodynamic parameters have been determined by 2D NMR and van't Hoff analysis and supported by computational study.

Do Depressive Symptoms Moderate the Effects of Exercise Self-efficacy on Physical Activity Among Patients With Coronary Heart Disease?

BACKGROUND: Exercise self-efficacy is an important predictor of physical activity. Patients with coronary heart disease are at risk of developing depressive symptoms that could further weaken their self-efficacy and interfere with their ability to engage in physical activity. OBJECTIVE: The aim of this study was to examine the relationship between depressive symptoms, exercise self-efficacy, and physical activity among patients with coronary heart disease and how the efficacy-activity relationship is affected by the patient's level of depression. METHODS: A survey was conducted on 149 participants at the time of discharge from the emergency and in-patient medical wards at 2 regional hospitals. RESULTS: The sample was mostly male, married, living with families, and of lower socioeconomic status. The mean exercise self-efficacy was 4.26 ± 2.73, and the median physical activity was 12 (interquartile range, 6-21). Approximately 26% of participants had high depressive symptoms. Those with more depressive symptoms reported lower self-efficacy scores and lower physical activity. In multivariate regressions, self-efficacy was an independent predictor of physical activity (b = 1.48, P < .001). After including depressive symptoms as the interaction term, exercise self-efficacy had a significantly stronger and positive relationship with physical activity (b = 0.14, P = .043). CONCLUSION: Exercise self-efficacy had a positive association with physical activity, and this relationship was stronger among coronary heart disease patients with depressive symptoms. This finding suggests that self-efficacy might be important in encouraging individuals with depressive symptoms to participate in physical activity. More efforts should target the development of effective strategies to improve exercise self-efficacy as a way of promoting physical activity among depressed coronary heart disease patients.

Synthesis of Luminescent Platinum(II) 2,6-Bis(N-dodecylbenzimidazol-2'-yl)pyridine Foldamers and Their Supramolecular Assembly and Metallogel Formation.

Dinuclear alkynylplatinum(II) metallofoldamers with an oligomeric m-phenyleneethynylene backbone have been designed with the incorporation of a sterically undemanding, π-conjugated, and hydrophobic 2,6-bis(N-dodecylbenzimidazol-2'-yl)pyridine pincer ligand. The complex with the optimal chain length has been found to exhibit gelation behavior via stabilization by noncovalent Pt···Pt and π-π stacking interactions in the hierarchical architecture constructed from the single-turn helix. The chain lengths of the complexes have been found to be a critical determinant for their gelation behavior, conformations, and morphologies. Such a gelation process has been found to undergo a cooperative assembly mechanism according to the nucleation-elongation model. Their self-assembly via the Pt···Pt and π-π stacking interactions has been studied by 1H NMR, 2D ROESY NMR (ROESY = rotating-frame Overhauser spectroscopy), electronic absorption, and emission spectroscopy, and density functional theory calculations have provided further insights into the folded state geometry of this class of metallofoldamers.

Photochromic Heterocycle-Fused Thieno[3,2-b]phosphole Oxides as Visible Light Switches without Sacrificing Photoswitching Efficiency.

A series of novel photochromic thieno[3,2-b]phosphole oxides has been shown to demonstrate photochromism without the need for the use of high-energy ultraviolet (UV) light irradiation while maintaining promising photochromic properties such as excellent thermal irreversibility, robust fatigue resistance, and high photoswitching efficiency. Promising visible light-induced photochromic properties have been realized by the new molecular design, in which various π systems have been incorporated into the weakly aromatic phosphole backbone instead of the conventional modification of the peripheral diaryl units that usually leads to a drastic reduction of the photochromic quantum yields (ϕO→C and ϕC→O < 0.01) or even a loss of the photochromic behavior. Excellent fatigue resistance has been observed for a representative compound with no apparent loss of photochromic reactivity over ten photochromic cycles by alternate irradiation with violet (ca. 410 nm) and green (ca. 500 nm) light with high photochromic quantum yields (ϕO→C = 0.87 and ϕC→O = 0.44), rendering it a new promising candidate as visible light photoswitches for various potential applications.

DFT Studies of Dimerization Reactions of Boroles.

Boroles undergo dimerization reactions to give Diels-Alder (DA) dimers, bridged-bicyclic (BB) dimers or spiro dimers (SD) depending on the substituents on the borole. We performed DFT calculations to investigate how different substituents at the carbon atoms of the butadiene backbone as well as at the boron atom influence the dimerization reaction pathways. The DFT results show that, in general, both the DA and BB dimers are easily accessible kinetically, and the DA dimers are thermodynamically more stable than the BB dimers. When the substituent-substituent repulsive steric interactions are alleviated to a certain extent, the BB dimers are more stable than the DA dimer, and become accessible. The SD dimers are generally kinetically difficult to obtain. However, we found that aryl substituents promote the formation of the SD dimers.

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.

Cleavage of a P-N Bond in a Urea-Containing (Ph2 P(R)PPh2 )-Bridged Dinuclear Gold(I) Thiolate Complex by Fluoride and a Mechanistic Insight.

A urea-containing, (Ph2 P(R)PPh2 )-bridged, dinuclear, gold(I) thiolate complex, [Au2 {Ph2 PN(C6 H4 OMe-4)PPh2 }(SC6 H4 NHCONHC6 H5 )2 ] (1) was designed and synthesized and its photophysical and anion recognition properties studied. The results show that 1 has a high selectivity toward F(-) . Upon addition of F(-) , the yellow solution was decolorized, and drastic changes of emission and (1) H and (31) P{(1) H} NMR signals were observed. Interestingly, these changes are attributed to fluoride-assisted P-N bond hydrolysis, instead of the expected hydrogen-bonding interactions with the urea receptor. Similar changes were observed for two other basic anions, AcO(-) and H2 PO4 (-) , but to a much lesser extent; and these anions were found to bind to the urea receptor at the same time. On the other hand, Cl(-) was found to only bind to the urea moiety through hydrogen-bonding interactions. Further studies with the control complex [Au2 {Ph2 PN(C6 H4 OMe-4)PPh2 }Cl2 ] (2) indicate that F(-) assists the hydrolysis process via cleavage of the P-N bond. DFT calculations were performed to study the reaction mechanism for the fluoride-assisted P-N bond hydrolysis of 2; these provide a better insight into the role of fluoride in the hydrolysis.

Photochromic dithienylethene-containing triarylborane derivatives: facile approach to modulate photochromic properties with multi-addressable functions.

A series of dithienylethene-containing triarylboranes has been designed, synthesized, and characterized. The electrochemistry, photophysics, and photochromic behavior have also been studied. The photophysical and photochromic properties could be facilely tuned in this system by varying the thiophene spacers (thiophene, thienothiophene, and bithiophene) between the dithienylethene and the dimesitylboron (BMes2 ) or the position of the BMes2 substitution in the thiophene spacers. The absorption of closed form has been found to be more sensitive towards the structural modification upon incorporation of the BMes2 unit. Moreover, multi-addressable photochromic reactivity is obtained upon addition of Lewis base (F(-) ), which is due to the formation of boron-Lewis base adduct. The dependence of the photophysical and photochromic properties on the thiophene spacers and the position of the BMes2 substitution has been further supported by computational studies.

A study on the effect of dianionic tridentate ligands on the radiative and nonradiative processes for gold(III) alkynyl systems by a computational approach.

Gold(III) alkynyl complexes with dianionic tridentate pincer ligands have received growing attention recently because of their rich luminescence behavior and their potential applications in areas such as optoelectronics and sensors. In this study, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed to investigate the radiative and nonradiative processes for the gold(III) alkynyl complexes with different dianionic tridentate ligands, [Au(C^N^C)(C≡CC6H5)] (1; C^N^C = 2,6-diphenylpyridine), [Au(C(Np)^N^C(Np))(C≡CC6H5)] [2; C(Np)^N^C(Np) = 2,6-di(2-naphthyl)pyridine], [Au(N^N^N)(C≡CC6H5)] [3; N^N^N = 2,6-bis(benzimidazol-2'-yl)pyridine], and [Au(C^C^N)(C≡CC6H5)] [4; C^C^N = 3-(2-pyridyl)biphenyl]. It has been found that the electronic properties of the tridentate ligand could have a significant impact on the radiative and nonradiative processes. This study provides an in-depth understanding on the effect of the dianionic pincer ligands on the different photophysical behaviors among the gold(III) alkynyl complexes and crucial information for the future design of gold(III) complexes in various applications.

A Solution-Processable Donor-Acceptor Compound Containing Boron(III) Centers for Small-Molecule-Based High-Performance Ternary Electronic Memory Devices.

A novel small-molecule boron(III)-containing donor-acceptor compound has been synthesized and employed in the fabrication of solution-processable electronic resistive memory devices. High ternary memory performances with low turn-on (V(Th1)=2.0 V) and distinct threshold voltages (V(Th2)=3.3 V), small reading bias (1.0 V), and long retention time (>10(4) seconds) with a large ON/OFF ratio of each state (current ratio of "OFF", "ON1", and "ON2"=1:10(3):10(6)) have been demonstrated, suggestive of its potential application in high-density data storage. The present design strategy provides new insight in the future design of memory devices with multi-level transition states.

A highly efficient silole-containing dithienylethene with excellent thermal stability and fatigue resistance: a promising candidate for optical memory storage materials.

Diarylethene compounds are potential candidates for applications in optical memory storage systems and photoswitchable molecular devices; however, they usually show low photocycloreversion quantum yields, which result in ineffective erasure processes. Here, we present the first highly efficient photochromic silole-containing dithienylethene with excellent thermal stability and fatigue resistance. The photochemical quantum yields for photocyclization and photocycloreversion of the compound are found to be high and comparable to each other; the latter of which is rarely found in diarylethene compounds. These would give rise to highly efficient photoswitchable material with effective writing and erasure processes. Incorporation of the silole moiety as a photochromic dithienylethene backbone also was demonstrated to enhance the thermal stability of the closed form, in which the thermal backward reaction to the open form was found to be negligible even at 100 °C, which leads to a promising candidate for use as photoswitchable materials and optical memory storage.

Design and synthesis of bipyridine platinum(II) bisalkynyl fullerene donor-chromophore-acceptor triads with ultrafast charge separation.

Donor-chromophore-acceptor triads, (PTZ)2-Pt(bpy)-C60 and ((t)BuPTZ)2-Pt(bpy)-C60, along with their model compound, (Ph)2-Pt(bpy)-C60, have been synthesized and characterized; their photophysical and electrochemical properties have been studied, and the origin of the absorption and emission properties has been supported by computational studies. The photoinduced electron transfer reactions have been investigated using the femtosecond and nanosecond transient absorption spectroscopy. In dichloromethane, (Ph)2-Pt(bpy)-C60 shows ultrafast triplet-triplet energy transfer from the (3)MLCT/LLCT excited state within 4 ps to give the (3)C60* state, while in (PTZ)2-Pt(bpy)-C60 and ((t)BuPTZ)2-Pt(bpy)-C60, charge-separated state forms within 400 fs from the (3)MLCT/LLCT excited state with efficiency of over 0.90, and the total efficiency with the contribution of (3)C60* is estimated to be 0.99. Although the forward electron transfer reactions are very rapid, the charge-separated state recombines to the singlet ground state at a time of hundreds of nanoseconds because of the difference in spin multiplicity between the charge-separated state and the ground state.

Synthesis, characterization, self-assembly, gelation, morphology and computational studies of alkynylgold(III) complexes of 2,6-bis(benzimidazol-2'-yl)pyridine derivatives.

A novel class of alkynylgold(III) complexes of the dianionic ligands derived from 2,6-bis(benzimidazol-2'-yl)pyridine (H2bzimpy) derivatives has been synthesized and characterized. The structure of one of the complexes has also been determined by X-ray crystallography. Electronic absorption studies showed low-energy absorption bands at 378-466 nm, which are tentatively assigned as metal-perturbed π-π* intraligand transitions of the bzimpy(2-) ligands. A computational study has been performed to provide further insights into the nature of the electronic transitions for this class of complexes. One of the complexes has been found to show gelation properties, driven by π-π and hydrophobic-hydrophobic interactions. This complex exhibited concentration- and temperature-dependent (1)H NMR spectra. The morphology of the gel has been characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

Computational studies on the excited states of luminescent platinum(II) alkynyl systems of tridentate pincer ligands in radiative and nonradiative processes.

Platinum(II) alkynyl complexes of various tridentate pincer ligands, [Pt(trpy)(C≡CR)](+) (trpy = 2,2':6',2″-terpyridine), [Pt(R'-bzimpy)(C≡CR)](+) (R'-bzimpy = 2,6-bis(N-alkylbenzimidazol-2'-yl)pyridine and R' = alkyl), [Pt(R'-bzimb)(C≡CR)] (R'-bzimb = 1,3-bis(N-alkylbenzimidazol-2'-yl)benzene and R' = C4H9), have been found to possess rich photophysical properties. The emission in dilute solutions of [Pt(trpy)(C≡CR)](+) originated from a triplet alkynyl-to-tridentate pincer ligand-to-ligand charge transfer (LLCT) excited state, with mixing of a platinum-to-tridentate pincer ligand metal-to-ligand charge transfer (MLCT) excited state, while that of [Pt(R'-bzimb)(C≡CR)] originated from a triplet excited state of intraligand (IL) character of the tridentate ligand mixed with a platinum-to-tridentate ligand MLCT character. Interestingly, both emissions were observed in [Pt(R'-bzimpy)(C≡CR)](+) in some cases. In addition, [Pt(R'-bzimb)(C≡CR)] displayed a photoluminescence quantum yield higher than that of [Pt(R'-bzimpy)(C≡CR)](+). Computational studies have been performed on the representative complexes [Pt(trpy)(C≡CPh)](+) (1), [Pt(R'-bzimpy)(C≡CPh)](+) (2), and [Pt(R'-bzimb)(C≡CPh)] (3), where R' = CH3 and Ph = C6H5, to provide an in-depth understanding of the nature of their emissive origin as well as the radiative and nonradiative processes. In particular, the factors governing the ordering of the triplet excited states and radiative decay rate constants of the emissive state ((3)ES) have been examined. The potential energy profiles for the deactivation process from the (3)ES via triplet metal-centered ((3)MC) states have also been explored. This work reveals for the first time the potential energy profiles for the thermal deactivation pathway of square planar platinum(II) complexes.

Synthesis, photochromic, and computational studies of dithienylethene-containing ß-diketonate derivatives and their near-infrared photochromic behavior upon coordination of a boron(III) center.

A series of dithienylethene-containing 1-thienyl-3-aryl-propane-1,3-diones (aryl = phenyl (Ph), thienyl (Th), and 4,5-bis(2,5-dimethylthiophen-3-yl)thiophen-2-yl (DTE-Th)) and the corresponding boron(III) diketonates, (O^O)BR(2) (R = F, C(6)F(5), and Ph), have been designed and synthesized. Their photophysical, electrochemical, and photochromic properties have been studied. Upon coordination of a boron(III) center, the closed forms of the dithienylethene-containing ß-diketonates show near-infrared response and the photochromic behavior was also found to be affected by the aryl substituents at the 3-position of the ß-diketonates. Moreover, computational studies have been performed that help to provide an understanding of the effect of substituents on the photophysical and photochromic properties.

Cholesterol-/estradiol-appended alkynylplatinum(II) complexes as supramolecular gelators: synthesis, characterization, photophysical and gelation studies.

A series of cholesterol-/estradiol-appended alkynylplatinum(II) complexes with tridentate N-donor ligands, based on 2,6-bis(1-alkylpyrazol-3-yl)pyridine, has been synthesized and characterized by (1)H NMR spectroscopy, FAB-mass spectrometry, and elemental analysis. Their photophysical properties have also been investigated. Computational studies have been performed to provide insights into the nature of the electronic transitions. Some of the complexes have been found to form stable thermo- and mechanoresponsive supramolecular gels.

Deep red to near-infrared emitting rhenium(I) complexes: synthesis, characterization, electrochemistry, photophysics, and electroluminescence studies.

A series of triarylamine-containing tricarbonyl rhenium(I) complexes, [BrRe(CO)3 (N^N)] (N^N=5,5'-bis(N,N-diaryl-4-[ethen-1-yl]-aniline)-2,2'-bipyridine), has been designed and synthesized by introducing a rhenium(I) metal center into a donor-π-acceptor-π-donor structure. All of the complexes showed an intense broad structureless emission band in dichloromethane at around 680-708 nm, which originated from an excited state of intraligand charge transfer ((3)ILCT) character from the triarylamine to the bipyridine moiety. Upon introduction of the bulky and electron-donating pentaphenylbenzene units attached to the aniline groups, the emission bands were found to be red shifted. The nanosecond transient absorption spectra of two selected complexes were studied, which were suggestive of the formation of an initial charge-separated state. Computational studies have been performed to provide further insight into the origin of the absorption and emission. One of the rhenium(I) complexes has been utilized in the fabrication of organic light-emitting diodes (OLEDs), representing the first example of the realization of deep red to near-infrared rhenium(I)-based OLEDs with an emission extending up to 800 nm.

Luminescent cyclometalated alkynylplatinum(II) complexes with a tridentate pyridine-based N-heterocyclic carbene ligand: synthesis, characterization, electrochemistry, photophysics, and computational studies.

A new class of luminescent alkynylplatinum(II) complexes with a tridentate pyridine-based N-heterocyclic carbene (2,6-bis(1-butylimidazol-2-ylidenyl)pyridine) ligand, [Pt(II)(C^N^C)(C≡CR)][PF6], and their chloroplatinum(II) precursor complex, [Pt(II)(C^N^C)Cl][PF6], have been synthesized and characterized. One of the alkynylplatinum(II) complexes has also been structurally characterized by X-ray crystallography. The electrochemistry, electronic absorption and luminescence properties of the complexes have been studied. Nanosecond transient absorption (TA) spectroscopy has also been performed to probe the nature of the excited state. The origin of the absorption and emission properties has been supported by computational studies.

Luminescent platinum(II) complexes of 1,3-bis(N-alkylbenzimidazol- 2'-yl)benzene-type ligands with potential applications in efficient organic light-emitting diodes.

A series of luminescent platinum(II) complexes of tridentate 1,3-bis(N-alkylbenzimidazol-2'-yl)benzene (bzimb) ligands has been synthesized and characterized. One of these platinum(II) complexes has been structurally characterized by X-ray crystallography. Their electrochemical, electronic absorption, and luminescence properties have been investigated. Computational studies have been performed on this class of complexes to elucidate the origin of their photophysical properties. Some of these complexes have been utilized in the fabrication of organic light-emitting diodes (OLEDs) by using either vapor deposition or spin-coating techniques. Chloroplatinum(II)-bzimb complexes that are functionalized at the 5-position of the aryl ring, [Pt(R-bzimb)Cl], not only show tunable emission color but also exhibit high current and external quantum efficiencies in OLEDs. Concentration-dependent dual-emissive behavior was observed in multilayer OLEDs upon the incorporation of pyrenyl ligand into the Pt(bzimb) system. Devices doped with low concentrations of the complexes gave rise to white-light emission, thereby representing a unique class of small-molecule, platinum(II)-based white OLEDs.

Synthesis and characterization of luminescent cyclometalated platinum(II) complexes of 1,3-bis-hetero-azolylbenzenes with tunable color for applications in organic light-emitting devices through extension of π conjugation by variation of the heteroatom.

A series of luminescent cyclometalated platinum(II) complexes of N^C^N ligands [N^C^N=2,6-bis(benzoxazol-2'-yl)benzene (bzoxb), 2,6-bis(benzothiazol-2'-yl)benzene (bzthb), and 2,6-bis(N-alkylnaphthoimidazol-2'-yl)benzene (naphimb)] has been synthesized and characterized. Two of the platinum(II) complexes have been structurally characterized by X-ray crystallography. Their electrochemical, electronic absorption, and luminescence properties have been investigated. In dichloromethane solution at room temperature, the cyclometalated N^C^N platinum(II) complexes exhibited rich luminescence with well-resolved vibronic-structured emission bands. The emission energies of the complexes are found to be closely related to the electronic properties of the N^C^N ligands. By varying the electronic properties of the cyclometalated ligands, a fine-tuning of the emission energies can be achieved, as supported by computational studies. Multilayer organic light-emitting devices have been prepared by utilizing two of these platinum(II) complexes as phosphorescent dopants, in which a saturated yellow emission with Commission International de I'Eclairage coordinates of (0.50, 0.49) was achieved.