A convenient synthesis of new isolable phosphaalkenes using the base-induced rearrangement of secondary vinylphosphines

The secondary vinylphosphines Ar(F)P(H)C(R)[double bond]CH(2) [2a, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = CH(3); 2b, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = C(6)H(5); 2c, Ar(F) = 2,4,6-(CF(3))(3)C(6)H(2), R = CH(3)] were prepared by treating the corresponding dichlorophosphine Ar(F)PCl(2) (1) with H(2)C[double bond]C(R)MgBr. In the presence of catalytic base (DBU or DABCO) the vinylphosphines (2a-c) undergo quantitative 1,3-hydrogen migration over 3 d to give stable and isolable phosphaalkenes Ar(F)P=C(R)CH(3) (3a, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = CH(3); 3b, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = C(6)H(5); 3c, Ar(F) = 2,4,6-(CF(3))(3)C(6)H(2), R = CH(3)). Under analogous conditions, only 90% conversion is observed in the base-catalyzed rearrangement of MesP(H)C(CH(3))[double bond]CH(2) to MesP[double bond]C(CH(3))(2). Presumably, the increase in acidity of the P-H group when electron-withdrawing groups are employed (i.e. 2a-c) favors quantitative rearrangement to the phosphaalkene tautomer (3a-c). Thus, the double-bond migration reaction is a convenient and practical method of preparing new phosphaalkenes with C-methyl substituents.     

Labelling and binding of poly-(L-lysine) to functionalised gold surfaces. Combined FT-IRRAS and XPS characterisation

We compare herein the interfacial reactivity of self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA), 1-undecanethiol (UDT) and 11-mercaptoundecanol (MUD) on gold surfaces towards aqueous solutions of poly-(L-lysine) (PL). Liquid-phase labelling of PL with the alkyne dicobalt hexacarbonyl cluster 1 combined with analysis of the substrates by Fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS) revealed that irreversible binding of PL occurred in all cases. However, the mechanism of binding involved differed markedly from one monolayer to the other. The main mode of interaction of PL to MUA SAM was of electrostatic nature between the terminal carboxylate of MUA and the ammonium groups of PL. For a similar number of bound thiolate molecules, the UDT adsorbed layer was found less continuous than the MUA one, allowing a higher fraction of PL to directly bind to the gold surface. As for MUD, very little thiolate molecules were adsorbed, leaving bare gold surface areas for non specific adsorption of PL.     

Visualizing the “heartbeat” of a city with tweets

Describing the dynamics of a city is a crucial step to both understanding the human activity in urban environments and to planning and designing cities accordingly. Here, we describe the collective dynamics of New York City (NYC) and surrounding areas as seen through the lens of Twitter usage. In particular, we observe and quantify the patterns that emerge naturally from the hourly activities in different areas of NYC, and discuss how they can be used to understand the urban areas. Using a dataset that includes more than 6 million geolocated Twitter messages we construct a movie of the geographic density of tweets. We observe the diurnal “heartbeat” of the NYC area. The largest scale dynamics are the waking and sleeping cycle and commuting from residential communities to office areas in Manhattan. Hourly dynamics reflect the interplay of commuting, work and leisure, including whether people are preoccupied with other activities or actively using Twitter. Differences between weekday and weekend dynamics point to changes in when people wake and sleep, and engage in social activities. We show that by measuring the average distances to a central location one can quantify the weekly differences and the shift in behavior during weekends. We also identify locations and times of high Twitter activity that occur because of specific activities. These include early morning high levels of traffic as people arrive and wait at air transportation hubs, and on Sunday at the Meadowlands Sports Complex and Statue of Liberty. We analyze the role of particular individuals where they have large impacts on overall Twitter activity. Our analysis points to the opportunity to develop insight into both geographic social dynamics and attention through social media analysis. © 2015 Wiley Periodicals, Inc. Complexity 21: 280–287, 2016     

Highlights on the recent advances in gold chemistry--a photophysical perspective

The presence of inter- and/or intra-molecular aurophilic interactions among the closed-shell gold(i) centres in various systems has been studied from various aspects, including synthetic, spectroscopic and theoretical approaches. The employment of different ligands can impose a significant influence on these factors and give rise to new complexes with interesting structural and photophysical properties. In this tutorial review, a number of recent examples are selected to illustrate the fascinating properties and chemistry, as well as versatility of gold(i) in these aspects and their potential applications to newcomers in this field. An emerging class of luminescent gold(iii) complexes is also described.     

Polyelectrolyte-induced self-assembly of positively charged alkynylplatinum(II)-terpyridyl complexes in aqueous media

Polyelectrolytes carrying multiple negative charges were found to induce the aggregation and self-assembly of the positively charged platinum(II)-terpyridyl complexes in aqueous media. The aggregation and self-assembly of the complexes were driven by electrostatic interactions between the polymer and the complex, and by terpyridine ligand pi-pi stacking and platinum-platinum (metal-metal) interactions. As a result, remarkable UV/Vis and emission spectral changes were observed. The spectroscopic property changes were related to the structural properties of the metal complexes as well as the polyelectrolytes. The induced self-assembly of the platinum complexes was also strongly affected by the solution properties of the aqueous media, for example, the solution pH, ionic strength, and the percentage of organic solvent added.     

Self-assembly, structures, and photophysical properties of 4,4'-bipyrazolate-linked metallo-macrocycles with dimetal clips

By employing functional diimine ligands coordinated dipalladium(II,II) or diplatinum(II,II) clips as corners and the coplanar 4,4'-bipyrazolate dianion (L(2-)) ligand as linker, a series of bipyrazolate-bridged metallo-macrocycles, namely, [M8L4](NO3)8 (M = Pd(dmbpy), 1; Pd(bpy), 2; Pt(bpy), 3a; Pd(phen), 4; Pt(phen), 5; Pd(15-crown-5-phen), 6; Pd(18-crown-6-phen), 8; Pd(benzo-24-crown-8-phen), 10a; Pt(15-crown-5-phen), 7a, Pt(18-crown-6-phen), 9a; Pt(benzo-24-crown-8-phen), 11a) and [M6L3](NO3)6 (M = Pt(bpy), 3b; Pt(15-crown-5-phen), 7b; Pt(18-crown-6-phen), 9b; Pd(benzo-24-crown-8-phen), 10b; Pt(benzo-24-crown-8-phen), 11b), have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the 1H-bipyrazolyl ligands in aqueous solution. All these compounds have a crown-shaped cavity that can serve as host to solvent molecules and anions. The structures are characterized by elemental analysis, (1)H and (13)C NMR, ESI-MS, and in the cases of 1a (the BF4(-) salt of 1), 2a (the BF4(-) salt of 2), and 3b by single-crystal X-ray diffraction analysis. Photophysical properties for complexes 1 and 2 are discussed.     

A Platinum(II) Terpyridine Metallogel with an L‐Valine‐Modified Alkynyl Ligand: Interplay of Pt⋅⋅⋅Pt, π–π and Hydrogen‐Bonding Interactions

A series of platinum(II) terpyridine complexes with L ‐valine‐modified alkynyl ligands has been synthesized. A complex with an unsubstituted terpyridine and one valine unit on the alkynyl is shown to be capable of gel formation, which is in sharp contrast to the gelation properties of the corresponding organic counterparts. Upon sol–gel transition, a drastic color change from yellow to red is observed, which is indicative of the involvement of Pt ??? Pt interactions. Through the concentration‐ and temperature‐dependent UV/Vis absorption, emission, circular dichroism, and ¹H NMR studies, the contribution of hydrogen bonding, Pt ??? Pt and π–π stacking interactions as driving forces for gelation have been established, and the importance of maintaining a delicate balance between different intermolecular forces has also been illustrated.     

Organic Photovoltaic Devices Based on a New Class of Oligothienylenevinylene Derivatives as Donor Materials

A new class of donor–acceptor‐containing oligothienylenevinylenes with a triphenylamine donor and a dicyanovinyl group as acceptor has been synthesized and characterized. By extending the oligothiophene backbone, both the optical bandgaps and the charge‐transport properties can be tuned. These oligothienylenevinylene derivatives show intense charge‐transfer absorption bands that cover the entire visible spectrum, with low optical bandgaps of approximately 1.64 eV. In addition, electrochemical studies reveal that these compounds possess relatively large ionization potentials of approximately 5.5 eV. On the basis of these newly developed dicyanovinyl‐substituted chromophores as donor materials and C₆₀ as acceptor material, bilayer organic photovoltaic devices have been fabricated, with the best device showing a high power conversion efficiency (PCE) of 2.0 %, with an open‐circuit voltage of 0.68 V and a fill factor of 0.60 after thermal annealing. The obvious morphology change with the formation of small domains in thin films and the reduction of series resistance are believed to be responsible for the dramatic performance improvement upon thermal annealing.     

Luminescent cyclometalated alkynylgold(III) complexes with 6-phenyl-2,2'-bipyridine derivatives: synthesis, characterization, electrochemistry, photophysics, and computational studies

A novel class of luminescent gold(III) complexes containing various tridentate cyclometalating ligands derived from 6-phenyl-2,2'-bipyridine and alkynyl ligands, [Au(RC^N^N)(C≡C-R')]PF(6), has been successfully synthesized and characterized. One of the complexes has also been determined by X-ray crystallography. Electrochemical studies show a ligand-centered reduction originated from the cyclometalating RC^N^N ligands as well as an alkynyl-centered oxidation. The electronic absorption and photoluminescence properties of the complexes have also been investigated. In acetonitrile at room temperature, the complexes show intense absorption at higher energy region with wavelength shorter than 320 nm, and a moderately intense broad absorption band at 374-406 nm, assigned as the metal-perturbed intraligand π-π* transition of the cyclometalating RC(∧)N(∧)N ligand, with some charge transfer character from the aryl ring to the bipyridine moiety. Most of the complexes have been observed to show vibronic-structured emission bands at 469-550 nm in butyronitile glass at 77 K, assigned to an intraligand excited state of the RC^N^N ligand, with some charge transfer character from the aryl to the bipyridyine moiety. Insights into the origin of the absorption and emission have also been provided by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations.     

Cyclometalated Iridium(III)–Polyamine Complexes with Intense and Long‐Lived Multicolor Phosphorescence: Synthesis,Crystal Structure,Photophysical Behavior,Cellular Uptake,and Transfection Properties

A new class of phosphorescent cyclometalated iridium(III)–polyamine complexes [{Ir(N^C)₂}_n(bPEI)](PF₆)_n (bPEI=branched poly(ethyleneimine), average M_w=25 kDa, n=15.6–27.4; HN^C=2‐phenylpyridine Hppy ( 1 a ), 2‐((1,1′‐biphenyl)‐4‐yl)pyridine Hpppy ( 2 a ), 2‐phenylquinoline Hpq ( 3 a ), 2‐phenylbenzothiazole Hbt ( 4 a ), 2‐(1‐naphthyl)benzothiazole Hbsn ( 5 a )) and [Ir(N^C)₂(en)](PF₆) (en=ethylenediamine; HN^C=Hppy ( 1 b ), Hpppy ( 2 b ), Hpq ( 3 b ), Hbt ( 4 b ), Hbsn ( 5 b )) have been synthesized and characterized. The X‐ray crystal structure of complex 5 b was also determined. All of these complexes showed a reversible iridium(IV/III) oxidation couple at +1.01 to +1.26 V and a quasi‐reversible ligand‐based reduction couple at ?1.54 to ?2.08 V (versus SCE). Upon photoexcitation, the complexes displayed intense and long‐lived green to orange–red emission in fluid solutions at room temperature and in low‐temperature glass. Lipophilicity measurements indicated that bPEI played a dominant role in the polar nature of complexes 1 a – 5 a , thus rendering them very soluble in aqueous solutions. Inductively coupled plasma–mass spectrometry (ICP‐MS) and confocal laser scanning microscopy (CLSM) data indicated that an energy‐requiring process, such as endocytosis, was involved in the cellular uptake of all of the complexes. In addition, the cytotoxicity of the complexes toward human cervix epithelioid carcinoma (HeLa) and human embryonic kidney 293T (HEK293T) cell‐lines has been evaluated by the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. The DNA‐binding properties of complex 5 a have been investigated by gel‐retardation assays and the polyplexes that were formed from this complex with plasmid DNA (pDNA) were studied by zeta‐potential measurements and particle‐size estimation. Furthermore, complex 5 a was grafted with poly(ethylene glycol) (PEG, average M_w=2 kDa) to different extents, thereby yielding the phosphorescent copolymers PEG_12.3‐g‐5 a , PEG_25.4‐g‐5 a , and PEG_62.1‐g‐5 a . Interestingly, these copolymers showed enhanced transfection activity, as revealed by in vitro transfection experiments with tissue‐culture‐based luciferase assays.