The Declining Market for Unionization, 1978

Article about union market, published by The Conference Board, Information Bulletin Number 44, August 1978

MEDIEVAL TREATIES AND THE DIPLOMATIC AESTHETIC

The charters of medieval diplomacy are essays in formulating a lingua franca of documentary communication. Through the process of realizing a mutually authentic textual object, they make negotiation visible. This essay examines some examples in detail from treaties concluded among England, France, and Portugal, in the context of a broader methodological intervention: to join the forces of New Diplomatic History with the study of material texts as visual culture

Laser Spectroscopy and Photodynamics of Alternative Nucleobases and Organic Dyes

Resonant excitation multiphoton ionization (REMPI) with TOF mass spectrometry detection was used to study and characterize organic chromophores which play a role in our prebiotic origins, the medicines we use, and in the paintings and other cultural artifacts we treasure.For our molecules which are prepared in a molecular beam (i.e. cold, neutral, and isolated) we are in the opportune position to compare with state of the art computation. This analysis was invaluable when differentiating alternative nucleobase structures in the chapters on isocytosine and 6-thioguanine, and understanding the effects of intramolecular hydrogen bonding environments when working with anthraquinone dyes. Of great interest was understanding excited state chromophore deactivation from low energy electronic states. The deactivation pathways a molecule takes, be them radiative or non-radiative, have severe implications on the form and function of that molecule. I continued to expand on the photostability centered hypothesis of prebiotic chemistry; that the aromaticity of genetic molecules leave them prone to harsh UV absorption in an ozone-less environment, however, a predisposition to convert electronic to ground state vibrational energy (heat) on an ultrafast timescale supports the prevalence of our canonical bases A, T, G, C, U. The work on isocytosine is exciting both in analogy to biological (keto) G and as a possible xeno or pre-RNA/DNA nucleobase (when paired with complimentary isoguanine). Secondly, 6-thioguanine converts with near unity to a long lived dark state and due to the thiooxo guanine substitution this intersystem crossing happens at an abnormally high rate. The work on anthraquinone dyes was an effort to understand the photostability of these molecules within their historical usage in cultural heritage materials and here I will present our case study on the these dyes and whether they undergo an excited state intramolecular proton transfer (ESIPT) to greatly reduce excited state lifetimes, promoting colorfastness as a function of structure

Corporate Citizenship in the New Century: Accountability, Transparency, and Global Stakeholder Engagement

This report from the Conference Board Working Group and Research Forum on Global Corporate Citizenship raises several issues for research and study; it aims at defining corporate citizenship leadership, and discusses how to manage citizenship in a global company. It examines corporate philanthropic programmes and activities through case studies and reporting citizenship practices

Photoproducts of the Photodynamic Therapy Agent Verteporfin Identified via Laser Interfaced Mass Spectrometry

Verteporfin, a free base benzoporphyrin derivative monoacid ring A, is a photosensitizing drug for photodynamic therapy (PDT) used in the treatment of the wet form of macular degeneration and activated by red light of 689 nm. Here, we present the first direct study of its photofragmentation channels in the gas phase, conducted using a laser interfaced mass spectrometer across a broad photoexcitation range from 250 to 790 nm. The photofragmentation channels are compared with the collision-induced dissociation (CID) products revealing similar dissociation pathways characterized by the loss of the carboxyl and ester groups. Complementary solution-phase photolysis experiments indicate that photobleaching occurs in verteporfin in acetonitrile; a notable conclusion, as photoinduced activity in Verteporfin was not thought to occur in homogenous solvent conditions. These results provide unique new information on the thermal break-down products and photoproducts of this light-triggered drug

Sodium cationization can disrupt the intramolecular hydrogen bond that mediates the sunscreen activity of oxybenzone

A key decay pathway by which organic sunscreen molecules dissipate harmful UV energy involves excited-state hydrogen atom transfer between proximal enol and keto functional groups. Structural modifications of this molecular architecture have the potential to block ultrafast decay processes, and hence promote direct excited-state molecular dissociation, profoundly affecting the efficiency of an organic sunscreen. Herein, we investigate the binding of alkali metal cations to a prototype organic sunscreen molecule, oxybenzone, using IR characterization. Mass-selective IR action spectroscopy was conducted at the free electron laser for infrared experiments, FELIX (600-1800 cm-1), on complexes of Na+, K+ and Rb+ bound to oxybenzone. The IR spectra reveal that K+ and Rb+ adopt binding positions away from the key OH intermolecular hydrogen bond, while the smaller Na+ cation binds directly between the keto and enol oxygens, thus breaking the intramolecular hydrogen bond. UV laser photodissociation spectroscopy was also performed on the series of complexes, with the Na+ complex displaying a distinctive electronic spectrum compared to those of K+ and Rb+, in line with the IR spectroscopy results. TD-DFT calculations reveal that the origin of the changes in the electronic spectra can be linked to rupture of the intramolecular bond in the sodium cationized complex. The implications of our results for the performance of sunscreens in mixtures and environments with high concentrations of metal cations are discussed

Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone

Avobenzone (AB) is a widely used UVA filter known to undergo irreversible photodegradation. Here, we investigate the detailed pathways by which AB photodegrades by applying UV laser-interfaced mass spectrometry to protonated AB ions. Gas-phase infrared multiple-photon dissociation (IRMPD) spectra obtained with the free electron laser for infrared experiments, FELIX, (600–1800 cm–1) are also presented to confirm the geometric structures. The UV gas-phase absorption spectrum (2.5–5 eV) of protonated AB contains bands that correspond to selective excitation of either the enol or diketo forms, allowing us to probe the resulting, tautomer-dependent photochemistry. Numerous photofragments (i.e., photodegradants) are directly identified for the first time, with m/z 135 and 161 dominating, and m/z 146 and 177 also appearing prominently. Analysis of the production spectra of these photofragments reveals that that strong enol to keto photoisomerism is occurring, and that protonation significantly disrupts the stability of the enol (UVA active) tautomer. Close comparison of fragment ion yields with the TD-DFT-calculated absorption spectra give detailed information on the location and identity of the dissociative excited state surfaces, and thus provide new insight into the photodegradation pathways of avobenzone, and photoisomerization of the wider class of β-diketone containing molecules

Excited state intramolecular proton transfer in hydroxyanthraquinones: Toward predicting fading of organic red colorants in art.

Compositionally similar organic red colorants in the anthraquinone family, whose photodegradation can cause irreversible color and stability changes, have long been used in works of art. Different organic reds, and their multiple chromophores, suffer degradation disparately. Understanding the details of these molecules' degradation therefore provides a window into their behavior in works of art and may assist the development of improved conservation methods. According to one proposed model of photodegradation dynamics, intramolecular proton transfer provides a kinetically favored decay pathway in some photoexcited chromophores, preventing degradation-promoting electron transfer (ET). To further test this model, we measured excited state lifetimes of substituted gas-phase anthraquinones using high-level theory to explain the experimental results. The data show a general structural trend: Anthraquinones with 1,4-OH substitution are long-lived and prone to damaging ET, while excited state intramolecular proton transfers promote efficient quenching for hydroxyanthraquinones that lack this motif

Probing the electronic relaxation pathways and photostability of the synthetic nucleobase Z via laser interfaced mass spectrometry.

The photostability of synthetic (unnatural) nucleobases is important in establishing the integrity of new genetic alphabets, and critical for developing healthy semisynthetic organisms. Here, we report the first study to explore the photostability and electronic decay pathways of the synthetic nucleobase, Z (6-amino-5-nitro-2(1 H)-pyridone), combining UV laser photodissociation and collisional dissociation measurements to characterise the decay pathways across the region from 3.1-4.9 eV. Photoexcitation across this region produced the m/ z 138 ion as the dominant photofragment, mirroring the dominant fragment produced upon higher-energy collisional excitation. Analysis of the ion-yield production curve profile for the m/ z 138 ion indicates that it is produced following ultrafast excited state decay with boil off of the OH functional group of Z from the hot electronic ground state. Electronic structure calculations provide physical insight into why this is the dominant fragmentation pathway, since a node in the electron density along the C-OH bond is found for all tautomers of Z. While the dominant decay pathway for Z is consistent with ultrafast excited state decay, we also identify several minor dissociative photochemistry decay pathways, associated with intrinsic photoinstability. The results presented here can be used to guide the development of more photostable synthetic nucleobases

A “one pot” tool for characterizing solution-phase and gas-phase photochemical reactions by electrospray mass spectrometry

The characterization of new photochemical pathways is important to progress the understanding of emerging areas of light-triggered inorganic and organic chemistry. In this context, the development of platforms to perform routine characterization of photochemical reactions remains an important goal for photochemists. Here, we demonstrate a new instrument that can be used to characterize both solution-phase and gas-phase photochemical reactions through electrospray ionization mass spectrometry (ESI-MS). The gas-phase photochemistry is studied by novel laser‐interfaced mass spectrometry (LIMS), where the molecular species of interest is introduced to the gas-phase by ESI, mass-selected and then subjected to laser photodissociation in the ion-trap. On-line solution-phase photochemistry is initiated by LEDs prior to ESI-MS in the same instrument with ESI-MS again being used to monitor photoproducts. Two ruthenium metal carbonyls, [Ru(η5-C5H5)(PPh3)2CO ][PF6] and [Ru(η5-C5H5)(dppe)CO][PF6] (dppe = 1,2-bis(diphenylphosphino)ethane) are studied using this methodology. We show that the gas-phase photofragmentation pathways observed for the ruthenium complexes via LIMS (i.e. loss of CO + PPh3 ligands from Ru(η5-C5H5)(PPh3)2CO ]+ and loss of just CO from [Ru(η5-C5H5)(dppe)CO]+, mirror the solution-phase photochemistry. The advantages of performing the gas-phase and solution-phase photochemical characterizations in a single instrument are discussed