Organic Connectors Research Articles

Rational Design, Synthesis, Purification, and Activation of Metal−Organic Framework Materials

The emergence of metal-organic frameworks (MOFs) as functional ultrahigh surface area materials is one of the most exciting recent developments in solid-state chemistry. Now constituting thousands of distinct examples, MOFs are an intriguing class of hybrid materials that exist as infinite crystalline lattices with inorganic vertices and molecular-scale organic connectors. Useful properties such as large internal surface areas, ultralow densities, and the availability of uniformly structured cavities and portals of molecular dimensions characterize functional MOFs. Researchers have effectively exploited these unusual properties in applications such as hydrogen and methane storage, chemical separations, and selective chemical catalysis. In principle, one of the most attractive features of MOFs is the simplicity of their synthesis. Typically they are obtained via one-pot solvothermal preparations. However, with the simplicity come challenges. In particular, MOF materials, especially more complex ones, can be difficult to obtain in pure form and with the optimal degree of catenation, the interpenetration or interweaving of identical independent networks. Once these two issues are satisfied, the removal of the guest molecules (solvent from synthesis) without damaging the structural integrity of the material is often an additional challenge. In this Account, we review recent advances in the synthetic design, purification, and activation of metal-organic framework materials. We describe the rational design of a series of organic struts to limit framework catenation and thereby produce large pores. In addition, we demonstrate the rapid separation of desired MOFs from crystalline and amorphous contaminants cogenerated during synthesis based on their different densities. Finally, we discuss the mild and efficient activation of initially solvent-filled pores with supercritical carbon dioxide, yielding usable channels and high internal surface areas. We expect that the advances in the synthesis, separation, and activation of metal-organic frameworks could lead to MOFs with new structures and functions, better and faster separation and purification of these materials, and processing methods that avoid pore blockage and pore collapse.

<i>Wired for War: The Robotics Revolution and Conflict in the Twenty-first Century</i> (review)

Reviewed by: Wired for War: The Robotics Revolution and Conflict in the Twenty-first Century John R. Pfeiffer P. W. Singer . Wired for War: The Robotics Revolution and Conflict in the Twenty-first Century. New York: Penguin, 2009. vi + 499 pp. Cloth, $17.00, ISBN: 9781594201981. Paperback, ISBN: 9780143116844. In one Clausewitzian sense war is a technique and policy of governance, and it follows that discussion of war can address utopian theorizing. There is an occasional fume of Clausewitz (invoked four or five times) in P. W. Singer's Wired for War, but Singer puts something in this book for everybody. The effects are of timeliness, disunity, shallowness, and disarming gravitas. The book describes a representative inventory of the new technologies for war and the dilemmas that use of such technology will precipitate. It is also part recruiting poster, part a manipulation of the popular perception of how tax dollars are being spent to enable the continued prosecution of war, and part elegy. Its cover proclaims " New York Times bestseller" (although my back-check couldn't verify this), and it is reviewed in about sixty forums. Wired is timely. Singer's agenda is associated with the Army-sponsored report in late 2009 on neuroscience research on pharmaceutical "fatigue countermeasures" to speed up the physiological repair accomplished in normal human sleep spans, to shorten the spans, "for a payoff in battle [that] would be enormous" (William Saletan, "You: The Updated Owner's Manual," New York Times Book Review, 2 August 2009, 23). It is also related to Mary Favret's War at a Distance: Romanticism and the Making of Modern Wartime (Princeton, 2009). Wired is also, by the way, far better than Charles E. Gannon's Rumors of War and Infernal Machines: Technomilitary Agenda-Settings in American and British Speculative Fiction (Rowman and Littlefield, 2003; reviewed in Utopian Studies 17, no. 3 [June 2006]: 551-53), which Singer does not mention. Serendipitously, Daniel Mendelsohn's analysis of James Cameron's 2010 film Avatar (New York Review, 25 March 2010, 10-12) helps us [End Page 375] understand Wired. Mendelsohn believes that Avatar 's alien "Na'vi—with their uniformly superb, sleekly blue-gleaming physiques, their weirdly infallible surefootedness, their organic connector cables, their ability to upload and download consciousness itself—are the ultimate expression of [Cameron's] career-long striving to make flesh mechanical. . . . [The Na'vi are] both admirably precivilized and admirably hypercivilized" (12). In short, the Na'vi are what cyborgs would be if they were organic. Wired is shallow. It covers a lot: "It will cover everything from [part 1—nine chapters] the resulting shifts in how wars are fought [by digitalized mechanisms] and who [still humans] is fighting them to [part 2—thirteen chapters] important questions that our new machine creations are starting to raise in politics, law, and ethics. War just won't be the same" (41). Part 1, "The Change We Are Creating," has chapter titles such as "Introduction: Scenes from a Robot War," "Robotics for Dummies," "To Infinity and Beyond: The Power of Exponential Trends," "Coming Soon to a Battlefield Near You: The Next Wave of Warbots," and "What Inspires Them: Science Fiction's Impact on Science Reality." Part 2, "What Change Is Creating for Us," has chapters titled "'Advanced' Warfare: How We Might Fight with Robots," "Open-Source Warfare: College Kids, Terrorists, and Other New Uses of Robots at War," "The Psychology of Warbots," "Changing the Experience of War and the Warrior," "Digitizing the Laws of War and Other Issues of (Un)Human Rights," "A Robot Revolt? Talking About Robot Ethics," and " Conclusion: The Duality of Robots and Humans." Wired could be an outline for a scholarly conference. There are a number of reservations we can have about the book. Its premise is not seriously original. It is a survey of current and theoretical digital technology designed for military actions by the United States and a summary of the highly predictable social, political, and legal problems that will result from this in the next half century. It repeats the facile claim that science fiction is an important predictor of and source of inspiration for future technological developments. Science fiction does not do this...

Ordered fabrication of luminescent multilayered thin films of CdSe quantum dots

The surface of CdSe nanoparticles was functionalized with 11-hydroxyundecanoic acid (11-HUDA) during in situ preparation to afford stable and highly luminescent quantum dot (QD) solutions. The reactivity of the hydroxyl groups of 11-HUDA was then utilized in carbamate bond forming reactions with diisocyanate-bearing molecules that serve as linkers in the fabrication of the multilayered CdSe quantum dot films. The covalent bond formation readily proceeds at ambient temperature and results in a layer-by-layer formation of thin films comprised of photoluminescent CdSe nanoparticles separated by long chain organic connectors. The successive layer-by-layer approach can be repeated multiple times to get the desired thickness of QD films on glass or silicon substrates. The atomic force microscopy indicated the successful attachment of the QDs on the substrate surface. Importantly, the in situ functionalized CdSe nanoparticles preserve their stable and highly photoluminescent optical properties in the resulting multilayered films. Moreover, there is a gradual increase in the intensities of electronic absorption and photoluminescent bands of the QDs with increasing the number of layers, confirming successful fabrication of the multilayered films. The quantum yield (QY) of the 12-layered film was measured to be 6%. These findings are important for the development of QD-based optical, electronic and sensing devices that can harness the highly photoluminescent properties of these ordered and stable nanocomposite materials.

Trinuclear Cobalt Based Porous Coordination Polymers Showing Unique Topological and Magnetic Variety upon Different Dicarboxylate-like Ligands

One-pot solvothermal self-assembly is employed to prepare a series of Co3 based porous coordination polymers, viz. 1, [H2N(CH3)2]2[Co3(ip)4]·H2O, 2, [H2N(CH3)2]2[Co3(bdc)4]·(DMF)2, 3, [H2N(CH3)2]2[Co3(bpdc)4]·(CH3OH)2(DMF)1.5, where ip, bdc, bpdc, and DMF are 1,3-benzenedicarboxylate, 1,4-benzenedicarboxylate, 4,4′-biphenyldicarboxylate, and N,N′-dimethylformamide, respectively. Via different organic connectors such as ip, bdc, and bpdc, such Co3 molecular building blocks (MBB), [Co3(CO2)8]2−, are associated together to give a tunable 8-connected topological framework, viz. 42464 for 1, 36414576 for 2, and 36418536 for 3. Upon the geometry and the length of organic connectors, their corresponding porosity occupied by c counterions plus solvent molecules also can be tunable, for example, with the consideration of [H2N(CH3)2]+ counterions, the solvent-accessible volume is 460.2 A3 for 1, equal to 23.9% of the cell volume, 3320.4 A3 for 2, equal to 56.3% of the cell volume, 4107.2 A3 for 3, equal to 50% of t...

Framework materials assembled from magnesium carboxylate building units

Four coordination polymers containing magnesium metal nodes and di- or tricarboxylic acid organic connectors have been synthesised and structurally characterised with the aid of single crystal X-ray diffraction. Mg3(bdc)3(DMA)4 (1) and Mg3(bdc)3(EtOH)2 (2) were prepared from the 1 : 1 reaction of 1,4-benzenedicarboxylic acid (H(2)bdc) with Mg(NO3)2.6H2O in dimethylacetamide (DMA) or EtOH respectively. Both 1 and 2 contain tri-metallic magnesium carboxylate units which act as six-coordinate nodes for network construction. These tri-magnesium nodes are joined by the bdc ligands in 1 to give a 2D layered structure with coordinated DMA solvent molecules between the layers, whereas in 2 they stack end-on to form a novel 3D network containing 1D Mg carboxylate chains. Both 1 and 2 are moderately hygroscopic, and powder X-ray diffraction and thermogravimetric analysis studies show them to be interconvertible with Mg(bdc) and the hydrated complex Mg(bdc)(H2O)2 via a series of solid-state reactions. Reaction of magnesium nitrate with 4,4'-biphenyldicarboxylic acid (H(2)bpdc) in DMA gives Mg3(bpdc)3(DMA)4 (3), which in contrast to 2 forms a 'squashed' 3D cubic network as a result of the increased distance between the trinuclear nodes necessitated by the longer bpdc ligands. Reaction of magnesium nitrate with the triangular organic building block 1,3,5-tricarboxylic acid (H(3)btc) in DMA gives crystals of Mg(H(1.5)btc)2/3(btc)1/3(DMA)2.(DMA)1/3 (4). Compound 4 contains mono-metallic metal nodes which assemble with the btc ligands to give 2D 6(3) tessellated layers with Mg-coordinated DMA molecules lying perpendicular to the layers. Some free DMA is also present in 4, sited in small pores between the layers.

Hydrogen Physisorption on the Organic Linker in Metal Organic Frameworks: Ab Initio Computational Study

Research for materials offering efficient hydrogen storage and transport has recently received increased attention. Metal organic frameworks (MOFs) provide one promising group of materials where several recent advances were reported in this direction. In this computational study ab initio methods are employed to study the physisorption of hydrogen on conjugated systems. These systems are used as models for the organic linker within MOFs. Here, we focus on the adsorption sites related to the organic linker with special attention to the edge site, which was only recently reported to exist as the weakest adsorbing site in MOFs. We also investigate chemically modified models of the organic connector that result in enforcing this adsorption site. This may be crucial for improving the uptake properties of these materials to the goal defined by DOE for efficient hydrogen transport materials.

23.3: Distinguished Paper: High-Efficiency Tandem Blue OLEDs

Tandem blue OLEDs using different fluorescent dopants have achieved 20 cd/A (CIEx,y = 0.14, 0.18) and 38 cd/A (CIEx,y = 0.15, 0.42) with external quantum efficiencies higher than 11%. The tandem blue OLEDs include two electroluminescent units that are connected in series with an organic intermediate connector. At an initial brightness of 1,000 cd/m2, the drive voltage of the devices can be less than 6.5 V, and the operational lifetime (T 50) of the devices is estimated to be greater than 10,000 h. We also demonstrate that the selection of electron-transporting material and an intermediate connector have significant impact on the electroluminescence performance of the tandem blue OLEDs.

Coordination Polymers Based on Inorganic Lanthanide(III) Sulfate Skeletons and an Organic Isonicotinate N-oxide Connector: Segregation into Three Structural Types by the Lanthanide Contraction Effect

Fourteen three-dimensional coordination polymers of general formula [Ln(lNO)(H2O)(SO4)]n, where Ln = La, 1.La; Ce, 2.Ce; Pr, 3.Pr; Nd, 4.Nd; Sm, 5.Sm; Eu, 6.Eu; Gd, 7.Gd; Tb, 8.Tb; Dy, 9.Dy; Ho, 10.Ho; Er. 11.Er; Tm, 12.Tm; Yb, 13.Yb; and Lu, 14.Lu; INO = isonicotinate-N-oxide, have been synthesized by hydrothermal reactions of Ln3+, MnCO3, MnSO4 x H2O, and isonicotinic acid N-oxide (HINO) at 155 degrees C and characterized by single-crystal X-ray diffraction, IR, thermal analysis, luminescence spectroscopy, and the magnetic measurement. The structures are formed by connection of layer, chain, or dimer of Ln-SO4 by the organic connector, INO. They belong to three structural types that are governed exclusively by the size of the ions: type I for the large ions, La, Ce, and Pr; type II for the medium ions, Nd, Sm, Eu, Gd, and Tb; and type III for the small ions, Dy, Ho, Er, Tm, Yb, and Lu. Type I consists of two-dimensional undulate Ln-sulfate layers pillared by INO to form a three-dimensional network. Type II has a 2-fold interpenetration of "3D herringbone" networks, in which the catenation is sustained by extensive pi-pi interactions and O-H...O and C-H...O hydrogen bonds. Type III comprises one-dimensional chains that are connected by INO bridges, resulting in an alpha-Po network. The progressive structural change is due to the metal coordination number decreasing from nine for the large ions via eight to seven for the small ions, demonstrating clearly the effect of lanthanide contraction. The sulfate ion acts as a micro4- or micro3-bridge, connecting two, three, or four metals, and is both mono- and bidentate. The INO ligand acts as a micro3- or micro2-bridge with carboxylate group in syn-syn bridging or bidentate chelating mode. The materials show considerably high thermal stability. The magnetic properties of 4.Nd, 6.Eu, 7.Gd, and 13.Yb and the luminescence properties of 6.Eu and 8.Tb are also investigated.

Controlling the torsion angle via adventitious cation binding

We report herein the synthesis of a linear binuclear ruthenium(II) complex, and the corresponding free ligand, for which the organic connector is a geometrically-constrained crown ether that binds added cations.

Polyhalogenides of BEDT-TTF and its derivatives: low-dimensional organic connectors

Polyhalogenides of BEDT-TTF and its derivatives: low-dimensional organic connectors

Effects of Vapors from Phenol Boards and Connector Lubricants on Activation of Wire Spring Relay Contacts

An unexamined trouble source for open relay contacts is addressed, i.e., that lubricants on connector systems used in the vicinity of open relays can contribute organic vapors which can cause excessive arcing behavior on the contacts. The contact activating ability of some organic connector lubricants and a phenol fiber printed wiring board have been examined. In spite of the relatively low (~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> Pa (1 Pa = 7.5 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> torr)) vapor pressures at room temperature, significant arc duration enhancement, and thus reduced life, was observed on palladium and palladium/silver relay contacts operating in air-lubricant gas mixtures at part per trillion levels. Operation in mixtures of lubricant wax vapor and the phenolic vapor from the boards showed an activation characteristic identical to that of the wax alone even though its concentration was approximately four orders of magnitude less than the phenol. Substantial reductions of contact life have been computed for some operating situations. A relationship between the number of carbon atoms in the activating organic molecule and the lower critical exposure for activation is observed. The larger the molecule, the lower the exposure required to activate contacts.