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Experimental And Theoretical Studies Of Tetramethoxy-p-benzoquinone: Infrared Spectra, Structural And Lithium Insertion Properties

Friday, December 20th, 2013

Published earlier this year in RSC Advances (RSC Adv., 2013, 3, 19081-19096), a follow-up (for my part) to the study The Low-/Room-temperature Forms Of The Lithiated Salt Of 3,6-dihydroxy-2,5-dimethoxy-p-benzoquinone: A Combined Experimental And Dispersion-Corrected Density Functional Study in CrystEngComm last year. The theoretical section for this paper is a tour-de-force of Crystal09 solid-state optimizations, density functional and dispersion-correction dependence, and post-processing using Carlo Gotti’s TOPOND software. In brief, the combination of vibrational spectra, electochemical measurements, and solid-state density functional theory tests are used to predict the structure of the previously unknown lithiated tetramethoxy-p-benzoquinone structure based on the good-to-excellent agreement with two known TMQ crystal structures (the testing of density functionals and dispersion corrections being a very good survey of the pros and cons of the varied methods. If you were pondering an approach to follow to perform the same kind of theoretical analysis, the procedure set up by Gaëtan and Christine in this paper is fully worth your consideration).

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Gaëtan Bonnard, Anne-Lise Barrès, Yann Danten, Damian G. Allis, Olivier Mentré, Daniele Tomerini, Carlo Gatti, Ekaterina I. Izgorodina, Philippe Poizot and Christine Frayret*

In the search for low-polluting electrode materials for batteries, the use of redox-active organic compounds represents a promising alternative to conventional metal-based systems. In this article we report a combined experimental and theoretical study of tetramethoxy-p-benzoquinone (TMQ). In carbonate-based electrolytes, electrochemical behaviour of this compound is characterized by a reversible insertion process located at approximately 2.85 V vs. Li+/Li0. This relatively high potential reactivity, coupled with our effort to develop computational methodologies in the field of organic electrode materials, prompted us to complement these experimental data with theoretical studies performed using density functional theory (DFT). Single crystals of TMQ were synthesized and thoroughly characterized showing that this quinonic species crystallised in the P21/n space group. The experimental crystal structure of TMQ was then used to assess various DFT methods. The structural features and vibrational spectra were thus predicted by using as a whole five common density functionals (PBE, LDA, revPBE, PBEsol, B3PW91) with and without a semi-empirical correction to account for the van der Waals interactions using either Grimme’s (DFT-D2) or Tkatchenko–Scheffler (TS) scheme. The most reliable combination of the DFT functional and the explicit dispersion correction was chosen to study the Li-intercalated molecular crystal (LiTMQ) with the view of indentifying Li insertion sites. A very close agreement with the experiment was found for the average voltage by using the most stable relaxed hypothetical LiTMQ structure. Additionally, a comparison of vibrational spectra gained either for TMQ molecule and its dimer in gas phase or through periodic calculation was undertaken with respect to the experimentally measured infrared spectra. The topological features of the bonds were also investigated in conjunction with estimates of net atomic charges to gain insight into the effect of chemical bonding and intermolecular interaction on Li intercalation. Finally, π-electron delocalization of both quinone and alkali salts of p-semiquinone were determined using the Harmonic Oscillator model of Aromaticity (HOMA) or aromatic fluctuation index (FLU) calculations.

Commensurate Urea Inclusion Crystals With The Guest (E,E)‐1,4-Diiodo-1,3-Butadiene

Friday, December 20th, 2013

Published in Crystal Growth & Design (Cryst. Growth Des., 2013, 13 (9), pp. 3852–3855) earlier this year. The theory work is less impressive than the successful crystal growth, with initial solid-state efforts in Crystal09 only very recently now producing good results (leaving the molecular calculations to Gaussian09 in this paper). The procedure leading to the observed crystal structure of this inclusion complex is a significant step in the direction of testing the theory proposed in Bond Alternation In Infinite Periodic Polyacetylene: Dynamical Treatment Of The Anharmonic Potential published earlier this year in J. Mol. Struct.

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Caption: Two views along the ba and ca crystal axes of the (E,E)‐1,4-Diiodo-1,3-Butadiene : Urea Inclusion Complex.

Amanda F. Lashua, Tiffany M. Smith, Hegui Hu, Lihui Wei, Damian G. Allis, Michael B. Sponsler, and Bruce S. Hudson

Abstract: The urea inclusion compound (UIC) with (E,E)-1,4-diiodo-1,3-butadiene (DIBD) as a guest (DIBD:UIC) has been prepared and crystallographically characterized at 90 and 298 K as a rare example of a commensurate, fully ordered UIC. The crystal shows nearly hexagonal channels in the monoclinic space group P21/n. The DIBD guest molecules are arranged end-to-end with the nonbonding iodine atoms in the van der Waals contact. The guest structure is compared with that for DIBD at 90 K and with computations for the periodic UIC and isolated DIBD molecule.

The 16-inch f/4.5 Collapsible-Truss Dobsonian From New Moon Telescopes – Feature Article In Astronomy Technology Today

Tuesday, June 25th, 2013

As first appeared on the CNY Observers & Observing website, www.cnyo.org, on 22 June 2013.

Greetings fellow astrophiles!

As if NEAF wasn’t already an excellent first showing for Ryan (and Heather!) Goodson and New Moon Telescopes (including discussions at Cloudy Nights (link 1, link 2) and a recorded observation in Sky & Telescope in this month’s issue), I am pleased to provide a full copy of the result of their first NEAF meeting with Gary Parkerson, Managing Editor of Astronomy Technology Today (www.astronomytechnologytoday.com): A feature (and cover) article (by yours truly) giving the NMT 16″ f/4.5 Dobsonian a complete walk-through in the May-June 2013 issue.

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Before anything else – I’d like to personally thank Gary and all at ATT for providing a platform for my review of the NMT scope, their continued support of other amateur astronomers through many years of excellent equipment reviews, and their complete coolness with allowing CNYO to repost the complete article for your viewing pleasure.


Click HERE For The Full Article (PDF, 2.3 MB)

From the article:

New Moon Telescopes (NMT, newmoontelescopes.com) is a very recent addition to the list of manufacturers of custom Dobsonians, having made their first company appearance at the Kopernik Winter Star Party (kopernik.org) this past January and their commercial appearance at NEAF 2013 this past April.

While NMT is now making itself known to the larger amateur astronomy community, NMT is no secret to Central New York observers. Amateur astronomers in several CNY astronomy clubs have seen the expert woodworking skills and design choices of NMT’s owner and sole craftsman, Ryan Goodson, first-hand, giving CNY observers and their always unpredictable weather conditions the honor of being NMT’s original customer base both in rebuilds and new Dobsonians.

The article introduction is no joke! There are three NMT Dobs owned just by CNYO session hosts alone (Larry S, Dan W, and myself), not counting whatever Ryan brings to our observing sessions, then several additional just in the CNY area (one CNY customer’s beautiful 18” Dob having been on display at NEAF). I remember just within the past ten years when SCTs and fancy mounts seemed to rule the observing grounds at Darling Hill Observatory, now all of the sessions I attend are populated by light buckets. The GOTO is increasingly being superseded in favor of memorization. I say excellent!

As a point of discussion in the article, I make reference to Ryan’s high-end component choices (the MoonLite focuser being high on the list – my “Ruby” (NMT #1) is named for its red focuser). I spent an extra block of time discussing the merits of a primary mirror purchase from John Lightholder at Lightholder Premium Optics.

Just as I have seen many an amateur astronomer start with seemingly decent eyepieces, then eventually sell and buy their way up to TeleVue (my personal bias, anyway), I have heard too many stories of observers with primary mirrors that eventually have their faults found out over the course of many observing sessions (the primary mirrors, that is). The solution, while not cheap, is simple – start with the best you can get and never, ever, find yourself regretting an “intermediate” purchase when you go to finally take the plunge on a high-quality primary.

The mirror alone cost more than many of the major vendors are currently charging for complete-and-shipped 12-inch Dobsonian telescopes. The reason is simple – it is absolutely worth it.

A final thought about the whole enterprise comes from Gary himself at ATT:

The Goodsons’ telescopes captured my attention, as did the Goodsons themselves, for the simple reason that they represent one of the aspects I love most about the telescope industry. Astronomy enthusiasts are primarily served by what are essentially cottage enterprises, populated with business people and craftsmen for whom their astro products and services represent labors of love. Most are family businesses, as is ATT, a fact that is reinforced with each trip to NEAF as I am privileged to again greet in person the family partnerships who gather there each year.

I am grateful to Gary and ATT for allowing us to repost the complete article on the CNYO website (and this pruned version of the issue was generated from the PDF I obtained as an enlightened subscriber to the digital version of ATT). It remains an excellent source of information from real users of equipment, a kind of completeness of analysis and discussion many of us had the pleasure of experiencing during discussions with Stu Forster and still have the pleasure of experiencing with my favorite local scope-sage Bob Piekiel.

And why yes, now that you mention it, it is easy to subscribe to ATT today! Click on the image below for more info!

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ChemMedChem Cover For April 2013 – Treating Type II Diabetes Through B12 Conjugation

Saturday, March 23rd, 2013

The back cover picture shows two views at 150 degree rotation of vitamin B12 conjugated to the potent anti- hyperglycemia peptide glucagon-like peptide-1 (GLP-1). The conjugate displays similar receptor binding and agonism to unconjugated GLP-1, including insulin potentiation from human transplant pancreatic islet cells, which bodes well for oral delivery of GLP-1 through the B12 dietary pathway. For more details, see the Communication by Robert P. Doyle et al. on p. 582 ff.

From the free press department… The cover for the April, 2013 issue of ChemMEDChem (just the cover art this time, no theoretical content in the associated article. All the theory’s figured out!). I’m still awaiting the journal’s posting of the article content but wanted to get something up in March. For related content, see the discussion on the “MedChemComm September 2012 Front Cover Image For The ‘Examining The Effects Of Vitamin B12 Conjugation…’ Paper” post or any of the B12-related posts on this site (www.somewhereville.com/index.php?s=b12). This work is similar in scope to the B12-insulin bioconjugate work in the previous studies, but now includes a different peptide (glucagon-like peptide-1) with similar properties.

The Low-/Room-temperature Forms Of The Lithiated Salt Of 3,6-dihydroxy-2,5-dimethoxy-p-benzoquinone: A Combined Experimental And Dispersion-Corrected Density Functional Study

Wednesday, November 21st, 2012

In press, in CrystEngComm (DOI:10.1039/C2CE26523). This is my first full paper completely internet-powered, in that I’ve not physically met any of the other co-authors (also in the internet-powered context, the recent paper on [18]-annulene was written and submitted without sharing a room with Dr. Bruce Hudson, but we’re in the same building, so it doesn’t quite count). Also, one of the few papers for which I had no image generation duties (a rare treat).

The discussion of the very interesting possibilities of molecular redox materials in lithium-ion batteries aside, this paper presents a very thorough example of the power of computational approaches to greatly improve the understanding of solid-state molecular materials by (specifically) 1: overcoming the hydrogen position identification problems inherent in X-ray diffraction methods, 2: reproducing the changes that come with temperature variations in molecular crystals and explaining the origins of those (possibly subtle) changes by way of dispersion-corrected density functional theory, and 3: demonstrating that the nature of intermolecular interactions (specifically hydrogen bonding) can be rigorously cataloged across varied materials using post-optimization tools (in this case, using Carlo Gatti’s excellent TOPOND program).

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Caption: Issue cover.

Gaëtan Bonnard, Anne-Lise Barrès, Olivier Mentré, Damian G. Allis, Carlo Gatti, Philippe Poizot and Christine Frayret*

Abstract

Following our first experimental and computational study of the room temperature (RT) form of the tetrahydrated 3,6-dihydroxy-2,5-dimethoxy-p-benzoquinone (LiM2DHDMQ⋅4H2O) compound, we have researched the occurrence of hydrogen ordering in a new polymorph at lower temperature. The study of polymorphism for the Li2DHDMQ⋅4H2O phase employs both experimental (single crystal X-ray diffraction) and theoretical approaches. While clues for disorder over one bridging water molecule were observed at RT (beta-form),a fully ordered model within a supercell has been evidenced at 100K (alpha-form) and is discussed in conjunction with the features characterizing the first polymorphic form reported previously. Density functional theory (DFT) calculations augmented with an empirical dispersion correction (DFT-D) were applied for the prediction of the structural and chemical bonding properties of the alpha and beta polymorphs of Li2DHDMQ·4H2O. The relative stability of the two polymorphic systems is evidenced. An insight into the interplay of hydrogen bonding, electrostatic and van der Waals (vdW) interactions in affecting the properties of the two polymorphs is gained. This study also shows how information from DFT-D calculations can be used to augment the information from the experimental crystal diffraction pattern and can so play an active role in crystal structure determination, especially by increasing the reliability and accuracy of H-positioning. These more accurate hydrogen coordinates allowed for a quantification of H-bonding strength through a topological analysis of the electron density (Atoms-in-molecules theory).

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