Progress on the synthesis and catalytic and anti‐migration properties of ferrocene‐based burning rate catalysts

Burning rate catalysts are of great importance in solid composite propellants for their unique property of accelerating combustion speed. Among various kinds of burning rate catalysts, ferrocene and its derivatives exhibit excellent catalytic effects and have become the most widely used burning rate catalysts. However, these simple ferrocenyl compounds trend to migrate in solid composite propellants during storage, which causes great damage to the propellants, equipment and environment and can even affect personal safety. The exploration of novel anti‐migratory ferrocene‐based compounds has become an advanced research hotspot in the field of burning rate catalysis. This review focuses on recent progress on the synthesis and catalytic properties of ferrocene‐based polymers and ferrocene derivatives as burning rate catalysts. Two main aspects of anti‐migratory exploration, i.e. synthesis of ferrocene‐based polymers and modification of the side groups of ferrocene, are summarized. Ferrocene‐based polymers can be obtained via condensation polymerization, addition polymerization, ring‐opening polymerization, polymer reactions, etc. Ferrocenyl compounds with active groups and ferrocene‐based metal coordination compounds were developed instead of the methods of lengthening the carbon chain of side groups and improving molecular polarity. Also, possible mechanisms of burning rate catalytic activity and migration are discussed and analyzed. Finally, the key points of the development of ferrocene‐based burning rate catalysts and solid composite propellants are proposed. Copyright © 2016 John Wiley & Sons, Ltd.     

Tris(2‐aminoethyl)amine‐based ferrocene‐terminated dendrimers as burning rate catalysts for ammonium perchlorate‐based propellant decomposition

Ferrocene‐based derivatives show potential application as burning rate catalysts (BRCs) for solid composite propellants. However, migration problems of simple ferrocene‐based derivatives limit their application as BRCs in solid composite propellants. To overcome the migration problems of ferrocene‐based BRCs and to enhance the burning rate of ammonium perchlorate (AP)‐based propellants, zero‐ to second‐generation tris(2‐aminoethyl)amine‐based ferrocene‐terminated dendrimers (G0, G1 and G2) were synthesized. The structures of G0, G1 and G2 were confirmed using ¹H NMR, Fourier transform infrared and UV–visible spectroscopies. The electrochemical behavior of G0, G1 and G2 was investigated using cyclic voltammetry. It was found that G0, G1 and G2 showed redox behavior due to the presence of ferrocene and this redox behavior was diffusion controlled over the investigated scan range. The burning rate catalytic effect of G0, G1 and G2 on thermal decomposition of AP was investigated using thermogravimetry and differential thermogravimetry. G0, G1 and G2 showed good catalytic effect on the thermal decomposition of AP. Anti‐migration studies showed that migration of G0, G1 and G2 was much slower than that of 2,2‐bis(ethylferrocenyl)propane (catocene) and ferrocene.     

Synthesis of ferrocene‐modified poly(glycidyl methacrylate) and its burning rate catalytic property

A series of ferrocene‐modified poly(glycidyl methacrylate) (PGMA‐Fc) compounds were synthesized and applied as burning rate catalysts in simulative solid propellant to overcome migration problems. ¹H NMR and Fourier transform infrared spectroscopies and gel permeation chromatography were used to characterize the synthesized polymers. Their electrochemical behavior was evaluated using cyclic voltammetry. Their catalytic performance for the decomposition of ammonium perchlorate (AP) was investigated using thermogravimetric analysis. Anti‐migration studies were conducted in migration tubes under 50°C. The results show that PGMA‐Fc has a good catalytic effect on lowering the thermal decomposition temperature of AP. Anti‐migration studies show that PGMA‐Fc has better anti‐migration performance than ferrocene and catocene.     

Synthesis and catalytic performance of ferrocene‐based compounds as burning rate catalysts

To overcome migration problems of ferrocene‐based burning rate catalysts and to enhance burning rate of ammonium perchlorate (AP)‐based propellants, eleven ferrocene‐based compounds ( 1 – 11 ) were synthesized by the condensation reaction of ferrocenecarbonyl chloride with corresponding amines and alcohols. The synthesis of 1 – 11 was confirmed using ¹H NMR, Fourier transform infrared and UV–visible spectroscopy. Their electrochemical properties were analyzed using cyclic voltammetry. The compounds showed redox behavior due to the presence of ferrocene. Their catalytic behavior in the thermal decomposition of AP was investigated using thermogravimetry (TG) and differential TG (DTG). In the presence of 5 wt% 1 – 11 , the thermal decomposition temperature of AP was significantly decreased. TG and DTG analyses showed that 1 – 11 had a good catalytic effect in the thermal decomposition of AP. Anti‐migration studies showed that migration of 1 – 11 was slower than that of 2,2‐bis(ethylferrocenyl)propane (catocene) and ferrocene. The effect of the presence of polar elements like oxygen and nitrogen on anti‐migration behavior of small ferrocene‐based compounds was also investigated. Oxygen‐containing compounds showed better anti‐migration behavior than nitrogen‐containing compounds.     

Thermal Decomposition Behavior and Non-isothermal Decomposition Reaction of Copper（ll） Salt of 4-Hydroxy-3,5-dinitropyridine Oxide and Its Application in Solid Rocket Propellant

The thermal decomposition behavior and kinetic parameters of the exothermic decomposition reactions of the title compound in a temperature‐programmed mode have been investigated by means of DSC, TG‐DTG and lower rate Thermolysis/FTIR. The possible reaction mechanism was proposed. The critical temperature of thermal explosion was calculated. The influence of the title compound on the combustion characteristic of composite modified double base propellant containing RDX has been explored with the strand burner. The results show that the kinetic model function in differential form, apparent activation energy E_a and pre‐exponential factor A of the major exothermic decomposition reaction are 1‐a,207.98 kJ*mol^?1 and 10^15.64 s^?1, respectively. The critical temperature of thermal explosion of the compound is 312.87 C. The kinetic equation of the major exothermic decomposition process of the title compound at 0.1 MPa could be expressed as: dα/dT=10^16.42 (1–α)e‐2.502×10⁴/T As an auxiliary catalyst, the title compound can help the main catalyst lead salt of 4‐hydroxy‐3,5dinitropyridine oxide to enhance the burning rate and reduce the pressure exponent of RDX‐CMDB propellant.     

First Synthesis of Ferrocenyl‐Substituted 1,2‐Dihydro‐2‐oxopyridine‐3‐carbonitriles

In the present investigation, the first incorporation of both ferrocene scaffold and 1,2‐dihydro‐2‐oxopyridine‐3‐carbonitrile pharmacophore leading to a series of structurally novel ferrocene‐based hybrids has been achieved, involving the condensation reaction of ferrocenyl substituted chalcones with 2‐cyanoacetamide in a freshly prepared EtONa solution at 70°. The molecular structures of these newly synthesized products were confirmed by IR, and ¹H‐ and ¹³C‐NMR analyses.     

Ferrocene‐tagged ionic liquid stabilized on silica‐coated magnetic nanoparticles: Efficient catalyst for the synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions

An advanced novel magnetic ionic liquid based on imidazolium tagged with ferrocene, a supported ionic liquid, is introduced as a recyclable heterogeneous catalyst. Catalytic activity of the novel nanocatalyst was investigated in one‐pot three‐component reactions of various aldehydes, malononitrile and 2‐naphthol for the facile synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions without additional co‐catalyst or additive in air. For this purpose, we firstly synthesized and investigated 1‐(4‐ferrocenylbutyl)‐3‐methylimidazolium acetate, [FcBuMeIm][OAc], as a novel basic ferrocene‐tagged ionic liquid. This ferrocene‐tagged ionic liquid was then linked to silica‐coated nano‐Fe₃O₄ to afford a novel heterogeneous magnetic nanocatalyst, namely [Fe₃O₄@SiO₂@Im‐Fc][OAc]. The synthesized novel catalyst was characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, and transmission and field emission scanning electron microscopies. Combination of some unique characteristics of ferrocene and the supported ionic liquid developed the catalytic activity in a simple, efficient, green and eco‐friendly protocol. The catalyst could be reused several times without loss of activity.     

Liquid‐crystalline azobenzene‐containing ferrocene‐based polymers: study on synthesis and properties of main‐chain ferrocene‐based polyesters with azobenzene in the side chain

Ferrocene‐based polymers are characterized by their electrochemical activity, good redox properties, thermal, photochemical stability, and liquid crystallinity, and thus they have various applications in different fields. A comprehensive investigation on the synthesis and properties of three novel main‐chain ferrocene‐based polyesters with azobenzene in the side chain (MFPAS) was carried out. The main‐chain ferrocene‐based polyester, poly(N‐phenyldiethanolamine 1,1′‐ferrocene dicarboxylate (PPFD), was synthesized via the solution polycondensation reaction of 1,1′‐ferrocenedicarbonyl chloride with phenyldiethanolamine (PDE). The novel MFPAS were synthesized via the post‐polymerization azo‐coupling reaction of PPFD with three different 4‐substituted anilines including 4‐nitroaniline, 4‐aminobenzoic acid, and 4‐aminobenzonitrile to produce 4‐nitrophenylazo‐functionalized‐PPFD (PPFD‐NT), 4‐carboxyphenylazo‐functionalized‐PPFD (PPFD‐CA), and 4‐cyanophenylazo‐functionalized‐PPFD (PPFD‐CN), respectively. All the synthesized polymers were characterized by ¹H NMR spectroscopy, Fourier transform infrared spectroscopy, and UV–visible spectroscopy. In addition, powder X‐ray diffraction patterns were measured for the synthesized polymers. The photoisomerization of the MFPAS was studied. The thermal properties of the MFPAS were studied using thermogravimetric analysis and differential scanning calorimetry. PPFD‐CA and PPFD‐CN were found to be more thermally stable than PPFD‐NT. Finally, the liquid‐crystalline properties of PPFD and the MFPAS were examined using polarized optical microscope. It was found that all the polymers possessed nematic phases and exhibited textures with schlieren disclinations. Copyright © 2012 John Wiley & Sons, Ltd.     

Ferrocenyl‐Modified DNA: Synthesis,Characterization and Integration with Semiconductor Electrodes

The ferrocenyl‐nucleoside, 5‐ethynylferrocenyl‐2′‐deoxycytidine ( 1 ) has been prepared by Pd‐catalyzed cross‐coupling between ethynylferrocene and 5‐iodo‐2′‐deoxycytidine and incorporated into oligonucleotides by using automated solid‐phase synthesis at both silica supports (CPG) and modified single‐crystal silicon electrodes. Analysis of DNA oligonucleotides prepared and cleaved from conventional solid supports confirms that the ferrocenyl‐nucleoside remains intact during synthesis and deprotection and that the resulting strands may be oxidised and reduced in a chemically reversible manner. Melting curve data show that the ferrocenyl‐modified oligonucleotides form duplex structures with native complementary strands. The redox potential of fully solvated ferrocenyl 12‐mers, 350 mV versus SCE, was shifted by +40 mV to a more positive potential upon treatment with the complement contrary to the anticipated negative shift based on a simple electrostatic basis. Automated solid‐phase methods were also used to synthesise 12‐mer ferrocenyl‐containing oligonucleotides directly at chemically modified silicon <111> electrodes. Hybridisation to the surface‐bound ferrocenyl‐DNA caused a shift in the reduction potential of +34 mV to more positive values, indicating that, even when a ferrocenyl nucleoside is contained in a film, the increased density of anions from the phosphate backbone of the complement is still dominated by other factors, for example, the hydrophobic environment of the ferrocene moiety in the duplex or changes in the ferrocene–phosphate distances. The reduction potential is shifted >100 mV after hybridisation when the aqueous electrolyte is replaced by THF/LiClO₄, a solvent of much lower dielectric constant; this is consistent with an explanation based on conformation‐induced changes in ferrocene–phosphate distances.     

One‐Pot Synthesis of Carbon‐Coated Nanostructured Iron Oxide on Few‐Layer Graphene for Lithium‐Ion Batteries

Nanostructure engineering has been demonstrated to improve the electrochemical performance of iron oxide based electrodes in Li‐ion batteries (LIBs). However, the synthesis of advanced functional materials often requires multiple steps. Herein, we present a facile one‐pot synthesis of carbon‐coated nanostructured iron oxide on few‐layer graphene through high‐pressure pyrolysis of ferrocene in the presence of pristine graphene. The ferrocene precursor supplies both iron and carbon to form the carbon‐coated iron oxide, while the graphene acts as a high‐surface‐area anchor to achieve small metal oxide nanoparticles. When evaluated as a negative‐electrode material for LIBs, our composite showed improved electrochemical performance compared to commercial iron oxide nanopowders, especially at fast charge/discharge rates.     

Ferrocenyl Ionic Compounds Based on 5‐Ferrocenyl‐1H‐tetrazole. Synthesis,Characterization, Migration,and Catalytic Effects During Combustion

Ferrocenyl ionic compounds, consisting of the 5‐ferrocenyltetrazolate anion and a guanidinium or a 1‐alkyl‐3‐methylimidazolium cation, were synthesized and characterized by ¹H NMR, ¹³C NMR, and UV/Vis spectroscopy, as well as elementary analysis. The molecular structures of four compounds were additionally confirmed by single‐crystal X‐ray diffraction. Results of the TG and DSC analyses showed that some compounds display high thermal stability. Cyclic voltammetry investigations suggested that the compounds exhibit redox waves for the ferrocenyl groups and are considered as irreversible redox systems. Migration studies revealed that migration trends of the compounds are much lower than that of 2, 2‐bis(ethylferrocenyl)propane (Catocene), extensively used in composite solid propellants. Their catalytic performances for thermal decomposition of ammonium perchlorate (AP), 1, 3,5‐trinitro‐1, 3,5‐triazacyclohexane (RDX), and 1, 2,5, 7‐tetranitro‐1, 3,5, 7‐tetraazacyclooctane (HMX) were evaluated by DSC and/or TG techniques. Most of the compounds exhibit high catalytic efficiency in the thermal degradation of AP and RDX. Those of the guanidine‐containing compounds 1 – 3 are better, implying that nitrogen‐rich moieties are beneficial to enhancing released heats of some energetic materials. These guanidine salts could be used as ferrocene‐based burning rate catalyst candidates in composite solid propellants.     

Ferrocenyl Ionic Compounds Containing [Fe(CN)6]3– Anions: Synthesis,Characterization, and Catalytic Effects during Combustion

Twenty‐eight novel ferrocenyl ionic compounds, composed of mononuclear 1‐ferrocenylmethylalkyldimethylammoniums, 1‐ferrocenylmethyl‐3‐alkylimidazoliums, or their dinuclear analogs and [Fe(CN)₆]^3– anion, were designed and synthesized to tackle significant volatility and migration tendency of ferrocene‐based burning rate catalysts (BRCs) used currently in the composite solid propellants. The new compounds were characterized by UV/Vis, FT‐IR, and elementary analysis. The crystal structures of compounds 2· 5H₂O and 3· CH₂Cl₂ · 4H₂O verified the successful preparation of the desired ionic compounds. The TG tests at 70 °C for 24 h revealed that the new compounds exhibit lower volatility than catocene. The cyclic‐voltammetry results suggested that new compounds are quasi‐reversible or irreversible redox systems. TheTG/DSC analyses exhibited that the compounds are of highly thermal stability. Their catalytic effects on the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), and 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazacyclooctane (HMX) were investigated. The results showed that most of the compounds exert great effects on the thermal degradation of AP and RDX during combustion. 11 and 2 are comparable to catocene in the thermal decomposition of AP and RDX, respectively, and can therefore be used as alternatives of catocene in a composite solid propellant. Some new compounds are unexpectedly active in promoting the thermal disintegration of HMX.     

Miscellaneous applications of ferrocene‐based peptides/amides

This article provides a critical review of the different applications of ferrocene‐based peptides/amides in biological as well as in non‐biological systems. Ferrocene‐based peptides/amides find many applications in different fields such as materials science, medicine, organic synthesis, bio‐organometallic and biological chemistry, asymmetric catalysis, nonlinear optics, in polymer science as redox active polymers and dendrimers, in molecular recognition as biosensors and in electrochemistry). Extensive research is being done on ferrocene‐based peptides/amides but we will highlight the various applications of ferrocene‐based peptides/amides for the period 2006–2010. The main factors that govern the potential biological and non‐biological applications are an electroactive core, a conjugated linker that can act as a chromophore and lower the oxidation potential of the ferrocene part, an amino acid or peptide derivative that can interact with other molecules via hydrogen bonding or any secondary bonding, and symmetric and asymmetric substitution on the ferrocene moiety. Copyright © 2011 John Wiley & Sons, Ltd.     

Stille Cross‐Coupling of a Racemic Planar‐Chiral Ferrocene and Crystallographic Trace Analysis of Catalysis Intermediates and By‐products

A pressure‐controlled procedure for the S_N1 reaction of rac‐1‐[(dimethylamino)methyl]‐2‐(tributylstannyl)ferrocene ( 1 ) to rac‐1‐(phthalimidomethyl)‐2‐(tributylstannyl)ferrocene ( 2 ) was developed. Pd⁰‐Catalyzed Stille coupling of 2 with iodobenzene afforded rac‐1‐phenyl‐2‐(N‐phthalimidomethyl)ferrocene ( 5 ) in 74% yield; after trace enrichment by crystallization of the combined mother liquors, one single crystal of each, 5 , catalysis intermediate trans‐iodo(σ‐phenyl)bis(triphenylarsino)palladium(II) ( 7 ), trans‐diiodobis(triphenylarsino)palladium(II) ( 8 ), and rac‐2,2′‐bis(phthalimidomethyl)‐1,1′‐biferrocene ( 9 ) could be isolated by crystal sorting under a microscope and characterized by X‐ray crystal structure analysis. Furthermore, 5 was deprotected to amine ( 11 ), which does even survive the Birch reduction to rac‐1‐(aminomethyl)‐2‐(cyclohexa‐2,5‐dienyl)ferrocene ( 12 ).     

Photoinduced Triplet–Triplet Energy Transfer in a 2‐Ureido‐4(1H)‐Pyrimidinone‐Bridged,Quadruply Hydrogen‐Bonded Ferrocene–Fullerene Assembly

2‐Ureido‐4(1H)‐pyrimidinone‐bridged ferrocene–fullerene assembly I is designed and synthesized for elaborating the photoinduced electron‐transfer processes in self‐complementary quadruply hydrogen‐bonded modules. Unexpectedly, steady‐state and time‐resolved spectroscopy reveal an inefficient electron‐transfer process from the ferrocene to the singlet or triplet excited state of the fullerene, although the electron‐transfer reactions are thermodynamically feasible. Instead, an effective intra‐assembly triplet–triplet energy‐transfer process is found to be operative in assembly I with a rate constant of 9.2×10⁵ s^?1 and an efficiency of 73 % in CH₂Cl₂ at room temperature.     

Ionic Ferrocenyl Coordination Compounds Derived from Imidazole and 1,2,4‐Triazole Ligands and Their Catalytic Effects During Combustion

Alkylferrocene‐based burning‐rate catalysts (BRCs) show conspicuous migration tendency and volatility during prolonged storage and fabrication process of a composite solid propellant. To enhance anti‐migration ability of the BRCs, forty novel ionic coordination compounds, [M(L)₄(H₂O)₂]_mX_n (M = Mn²⁺, Co²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Pb²⁺, Cr³⁺, Bi³⁺, or Cd²⁺; L = ferrocenylmethyl imidazole or ferrocenylmethyl‐1,2,4‐triazole; X = picrate or trinitroresorcinolate), were synthesized and characterized by FT‐IR, UV/Vis, and elementary analysis. Additionally, the crystal structures of six compounds were confirmed by single‐crystal X‐ray diffraction. The TG analyses revealed that the new compounds show high thermal stability. Cyclic voltammetry studies suggested that theyare irreversible redox systems. Their catalytic activities in the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclo‐hexane (RDX) and 1,2,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) were examined by DSC technique. The results indicated that all the new compounds exert great effects on the thermal decomposition of AP and RDX, among them some compounds are more active than catocene. Compound 26 has good catalytic ability in the thermal decomposition of HMX, representing a rare example of the reported ferrocene‐based BRCs which show catalytic activity during combustion of HMX.     

Field‐Effect Nanoparticle‐Based Glucose Sensor on a Chip: Amplification Effect of Coimmobilized Redox Species

A capacitive EIS (electrolyte‐insulator‐semiconductor) structure was modified with gold nanoparticles together with glucose oxidase and used as field‐effect‐based glucose biosensor using the constant capacitance mode. Co‐immobilization of ferrocene redox species resulted in a two‐fold increase of the biosensor sensitivity. The effect was explained by the hydrogen peroxide‐mediated oxidation of ferrocene resulting in a pool of charged species at the interface increasing the sensor response towards glucose. The studied approach was suggested as a general means to amplify signals from Si chip‐based field‐effect enzyme biosensors.     

Preparation,Properties, and Reactions of Metal‐Containing Heterocycles. CX [1] Crystal Structure of 1, 1'‐Bis{[4‐(1, 10‐phenanthroline‐3‐yl‐ethynyl)‐2, 5‐dipropoxy‐phenyl]ethynyl}ferrocene

The crystal structure of 1, 1'‐bis{[4‐(1, 10‐phenanthroline‐3‐yl‐ethynyl)‐2, 5‐dipropoxy‐phenyl]ethynyl}ferrocene ( 1 ) is reported. This compound crystallizes with two chloroform solvent molecules in the monoclinic space group P2₁/c (No. 14), a = 15.4253(11), b = 23.2003(10), c = 17.2630(13) Å, β = 90.866(9)° and Z = 4. Both arms of the ferrocene moiety are parallel displaced with the four nitrogen atoms pointing to the same direction.     

1,5‐Diamino‐4‐methyltetrazolium 5‐Nitrotetrazolate – Synthesis,Testing and Scale‐up

1,5‐Diamino‐4‐methyltetrazolium 5‐nitrotetrazolate ( 2b ) was synthesized in high yield from 1,5‐diamino‐4‐methyltetrazolium iodide ( 2a ) and highly sensitive silver 5‐nitrotetrazolate (AgNT). A safer synthesis, suitable for scale‐up, is introduced involving reaction of the previously unreported 1‐amino‐5‐imino‐4‐methyltetrazole free base ( 2 ) with ammonium 5‐nitrotetrazolate. Both new compounds ( 2 and 2b ) were fully characterized using vibrational (IR and Raman) and multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁴N, ¹⁵N), elemental analysis and single crystal X‐ray diffraction. The hydrogen‐bonding networks of both materials are described in terms of their graph‐sets. Compound 2b is hydrolytically stable with a high melting point and concomitant decomposition at 160 °C. The sensitivity of the energetic salt 2b towards impact (>30 J) and friction (>360 N) was tested. The constant volume energy of combustion (Δ_cU) of 2b was measured experimentally using bomb calorimetry. In addition, the detonation parameters (detonation pressure and velocity) of the nitrotetrazolate salt were calculated from the energy of formation, the crystal density and the molecular formula using the EXPLO5 computer code (P = 15.5·GPa, D = 6749 m s^?1) and are similar to that of TNT and nitroguanidine making 2b of prospective interest in propellant charge formulations or, in combination with a suitable oxidizer, as a solid propellant.     

Recent research progress in the synthesis,properties and applications of ferrocene‐based derivatives and polymers with azobenzene

Aromatic azobenzene derivatives are outstanding organic photochromic compounds that possess unique photochemical properties. These compounds are widely used in research and development for various applications, especially in information storage, owing to their ability to isomerize between cis (Z) and trans (E) forms under the influence of light of different wavelengths. On account of these advantages, many efforts have been made to generalize the use of azobenzene derivatives. Furthermore, ferrocene‐based polymers and derivatives are promising candidates for functional materials due to their unique redox properties. By interlinking ferrocene with azobenzene, novel functional materials can be obtained that will integrate the excellent properties of both and will provide new applications in various fields including information storage, ion recognition, molecular devices, etc. This article provides an overview of the synthesis, properties and applications of novel ferrocene‐based polymers and derivatives containing azobenzene units. Copyright © 2015 John Wiley & Sons, Ltd.