bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalytic Activity of Novel Vitamin B12 Derivatives
Authors: Gryko Dorota 
Published: February 2020

Among many biologically important metals, Co, in the form of vitamin B12 (cyano-cobalamin), plays a unique role. B12 coenzymes are indispensable for catalyzing enzymatic rearrangements (coenzyme B12, adenosylcobalamin) and methylation reactions (methylcobalamin).1 The special ability of vitamin B12 and other corrinoids to form a Co-C bond, combined with its facility in furnishing alkyl radicals via homolysis, has attracted the interest of many researchers, because corrinoids can be used as catalysts for C-C-bond forming reactions, which belong to the most challenging processes in organic synthesis. These catalytic reactions typically involve alkyl-cobalt complexes, which are formed in reactions of Co(I) species and an electrophile or a Co(II) and a radical. The most common chemical procedure utilizes the ‘supernucleophilicity’ of the Co(I) species (B12s) toward alkylating agents, such as alkyl halides. Homolysis of the Co-C bond generates a carbon-centered radical, which can, in situ, disproportionate, abstract H˙, or self-couple. In these reactions, B12 alkyl derivatives can be considered ‘reversible carriers’ of an alkyl radical.4

We have developed the synthesis of novel cobalamin derivatives possessing modified substituents at the periphery of the molecule. Our methodology presents a unique situation in which the six peripheral amide groups are transformed while leaving the bottom “f-loop” intact.2 These derivatives displayed UV-Vis spectra and oxidation-reduction characteristics similar to those of vitamin B12 but they differed significantly from the”incomplete” corrinoid heptamethyl cobyrinate, where the nucleotide moiety is absent, and instead, the second cyanide is coordinated. We confirmed that the intramolecular coordinating ligand plays a role in the radical reactions catalyzed by vitamin B12 derivatives. For example, the microwave-assisted homocoupling of benzylbromide3 catalyzed by cobalester produced a higher yield when compared to reactions catalyzed by reduced (CN)2Cob(OMe)7.Furthermore, the amphiphilic character of these newly synthesized derivatives facilitates carbon insertion into the vinyl C-H bond of olefins with alkyl diazoacetates in the presence of light.
1. Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999
2. Proinsias ó, K.; Giedyk, M.; Sharina, I.G.; Martin, E. and Gryko, D. ACS Med. Chem. Lett.
2012, 3, 476.
3. Giedyk, M.; Fedosov, S.; Gryko, D. Chem.
Commun.
2014, 50, 4674-4676.
4. Shey, J.; McGinley, Ch.M.; McCauley, K.M.; Dearth, A.S.; Young, B.T. and van der Donk, W.A. J. Org.
Chem.
2002, 67, 837.

Figure 1
Synthesis, Redox Properties and Structural Features of Expanded Isophlorins
Authors: Anand Venkataramanarao Govindan , Gopalakrishna Tullimilli Yadagiri 
Published: February 2020

The expanded derivatives of isophlorin provide sufficient examples for Huckel’s 4nπ anti-aromatic systems. They vary significantly in their electrochemical properties compared to the aromatic expanded porphyrins. In comparison to the small macrocycles, the large and planar expanded isophlorins exhibit reversible two-electron oxidation. The structure of these macrocycles also undergo reversible structural transformation between planar and figure of eight conformations accompanying the redox process. The oxidized product could be identified as aromatic dication or as a polaron pair depending on the size of the macrocycle. The number of non-pyrrolic heterocyclic units is crucial to stabilize aromatic, antiaromatic or neutral radical isophlorin. A stable 25π neutral radical identified in a one-pot synthesis, exhibits reversible one electron redox to form 24π anti-aromatic cation and a 26π aromatic anion. Synthesis, experimental details and structural features of expanded isophlorins will be highlighted in this presentation.
References:
1. T. Y. Gopalakrishna, J. S. Reddy and V. G. Anand, Angew. Chem. Int. Ed., 2013, 52, 1763.
2. T. Y. Gopalakrishna and V. G. Anand, Angew. Chem. Int. Ed., 2014, 53, 6678.
3. T. Y. Gopalakrishna, J. S. Reddy and V. G. Anand, Angew. Chem. Int. Ed., 2014, 53, 10984
Synthesis and Unique Spectroscopic Properties of Main Group Element Phthalocyanine and Tetraazaporphyrin Complexes
Authors: Kobayashi Nagao , Furuyama Taniyuki , Satoh Koh , Yoshida Takuya , Kushiya Tomofumi 
Published: February 2020

Phthalocyanines (Pcs) generally have strong absorption bands in the 650-680 nm region, which are referred to as the Q-bands and have been assigned to the transition between the HOMO and the LUMO of the Pc p-system. Although attempts to shift the Q-band to the near-IR region have been carried out by many researchers, nobody has so far succeeded in shifting the band beyond 1000 nm. To address this, Pcs with electron-donating group 16 (S, Se, and Te) atoms at the peripheral, so-called a positions, coordinating a group 15 (P, As, and Sb) ion, have been synthesized through a process of rational design based on a consideration of the size of MO coefficients in the frontier p-MOs [1]. The introduction of the group 16 elements at the a positions results in a red shift of the Q band from the 650-680 nm region to ca. 800 nm, due mainly to a destabilization of the HOMO. The introduction of group 15 elements in the +5 oxidation state to the central cavity results in a further red shift of the Q-band to the 1020-1060 nm region, due to a marked and moderate stabilization of the LUMO and HOMO, respectively (Fig. 1). In contrast, when group 15 (P, As) elements were coordinated by tetra-phenylated tetraazaporphyrins (TAPs), completely unexpected and highly unusual absorption bands were observed between the Soret and Q-band regions (Fig. 1). MO calculations carried out for a series of compounds with different substituents at the para-position of the phenyl groups predicted that these bands can be assigned to charge-transfer (CT) transitions from the peripheral aryl substituents to the TAP core.[2] Because of the presence of these CT bands, the TAPs in this study effectively absorb across the complete UV-visible region(300-700 nm) as single, discrete chromophores.
References: [1] Furuyama T, Sato K, Kushiya T, Kobayashi N. J. Am. Chem. Soc.2014; 136: 765-776. [2] Furuyama T, Yoshida T, Hashizume D, Kobayashi N. Chem. Sci. 2014; 5: 2466-2474.

Figure 1
Electrochemical Gating of Charge Transport in Single Macrocycle Molecular Switches
Authors: Borguet Eric 
Published: February 2020

Molecular switches, i.e., molecular scale devices that can be turned on and off, are of long standing interest. In the quest for miniaturization of electronic devices, the development of electrical switches of molecular dimensions has been identified as an important target of practical importance. While much progress has been made in designing functional molecular scale electrical switches, i.e., molecular cores whose intrinsic conductivity can be externally modulated, the question of contact resistance has not been sufficiently addressed.
Our novel strategy for the regulation of charge transport through single molecule junctions combines external stimuli using a variation of electrode potential in an electrochemical environment, internal modulation of molecular structures and optimization of anchoring groups. Our synthetic collaborators have designed redox-active benzodifuran (BDF) compounds as functional electronic units which we have used to fabricate metal-molecule-metal (m-M-m) junction devices by scanning tunneling microscopy (STM) and mechanically controllable break junctions (MCBJ).[1] The conductance of BDF terminated thiol, the standard anchoring group for molecular scale electronic components, can be tuned by changing the electrode potentials in an ionic liquid electrolyte to show a clear single molecule field effect transistor (FET) behavior.
We hypothesized that we could optimize the response by appropriate choice of molecular anchoring group.[2] Guided by our earlier investigations, a BDF molecule tailored with carbodithioate (-CS2-) anchoring groups was synthesized. Our studies show that replacement of thiol by carbodithioate not only increases the junction conductance, but also substantially improves the FET response by enhancing the on/off ratio from 2.5 to 8.
[1] Regulating a Benzodifuran Single Molecule Redox Switch via Electrochemical Gating and Optimization of Molecule/Electrode Coupling, Zhihai Li, Hui Li, Songjie Chen, Toni Froehlich, Christian Schönenberger, Michel Calame, Silvio Decurtins, Shi-Xia Liu and Eric Borguet, Journal of the American Chemical Society 136, 25 8867-8870 (2014).
[2] Optimizing Single-Molecule Conductivity of Conjugated Organic Oligomers with Conjugated Carbodithioate Linkers, Yangjun Xing, Tae-Hong Park, Ravindra Venkatramani, Shahar Keinan, David N. Beratan, Michael J. Therien, and Eric Borguet, Journal of the American Chemical Society 132 (23), 7946-7956 (2010).

Figure 1
Evaluation of Dezincification Corrosion of Brass By Electrochemical Impedance
Authors: Hoshi Yoshinao , Tabei Kozue , Shitanda Isao , Itagaki Masayuki 
Published: February 2020

The dezincification corrosion of the brass has been investigated to obtain the fundamental knowledge concerning the selective dissolution mechanisms. Pickering et al. (1-3) reported that a porous Cu-rich layer was formed on the brass surface due to the selective dissolution of Zn from brass. They classified the dissolution of the binary alloy into two types, which is the selective dissolution and simultaneous dissolution.
In the present work, we investigated the dissolution of brass by an electrochemical impedance spectroscopy (EIS). The EIS enables us to discriminate the time constants of elementary steps in the dissolution process. The Cu-enriched layer was formed on the brass surface by following method: The galvanostatic polarization of the brass was performed at 1.0 mA/cm2 for 24 h in the electrolyte solution of 0.5M NaCl containing 5mM NaHCO3. The temperature of the electrolyte solution was keep at 60 oC by thermostatic bath. In order to investigate the porous structure of the Cu-enriched layer formed on the brass surface due to dezincing, the impedance spectrum was measured to examine the current distributions within the pores. In addition, impedance and complex capacitance corresponding to the typical equivalent circuits involving a transmission line model (TLM) are discussed to propose the evaluation method for the dezincification of brass.
Reference
1. H. W. Pickering and C. Wagner, Journal of the Electrochemical Society, 114, 698 (1967).
2. H. W. Pickering, Journal of the Electrochemical Society, 115, 143 (1968).
3. H. W. Pickering and P. J. Byrne, Journal of the Electrochemical Society, 116, 1492 (1969).
Study of Cu Bimetallic Corrosion and Its Inhibition Strategy for Cu Interconnect Application Using Micro-Pattern Corrosion Screening
Authors: Chyan Oliver , Goswami Arindom , Koskey Simon , Yu Kyle 
Published: February 2020

Ru and other noble metals have been actively investigated for use as seedless liner/barrier materials for advanced Cu interconnect applications. Due to the lack of volatile byproducts in the reactive ion etching of Cu, the Cu interconnects are fabricated by dual damascene patterning process that involves etching a trench/via pattern into a dielectric, the blanket deposition of a diffusion barrier followed by Cu electroplating, and finally removal of Cu overburden by chemical-mechanical planarization (CMP). Since the CMP process exposes the Cu interconnect and metal barrier to the continual presence of corrosive chemicals, the resulting bimetallic corrosion between Cu and diffusion barrier metal can be detrimental to the overall production yields of integrated circuit devices. In this paper, we will present findings from a new corrosion screening metrology utilizing micro-corrosion test patterns (Cu dots, D≈130µm) to provide rapid in-situ corrosion evaluations in manufacture relevant chemical environments used to produce Cu interconnect structure. The results from Cu micro-pattern corrosion screening corroborate well with XPS and electrochemical techniques to reveal the detailed bimetallic corrosion mechanisms in specific chemical environments. For most of the CMP solutions studied to date, the Cu corrosion was found to be accelerated through an oxygen reduction reaction catalyzed by Ru. The new insights obtained from mechanistic investigation on Cu/Ru bimetallic corrosion not only help to unveil the real functions of each chemical previously masked by the complex matrix of CMP formulation, it also significantly expands the chemistry tool set that enables better corrosion inhibition strategy to protect detrimental corrosion defects of Cu interconnect with minute nanometer dimension used in advanced IC device. For example, micro-pattern corrosion screening results and electrochemical analyses revealed that 1mM pyrazole in 8 wt.% tetramethyl ammonium hydroxide (TMAH) solution could inhibit Cu corrosion more effectively than 10mM benzotriazole (BTA) in the same solution. Overall Cu corrosion rate in TMAH based highly alkaline post CMP cleaning solution is shown to be considerably reduced to <1Å/min by addition of pyrazole as corrosion inhibitor.
Growth of TiO2 Nanotube Layers on Ti Substrates with Different Microstructures
Authors: Kim Min Su , Yamamoto Shota , Tsuchiya Hiroaki , Fujimoto Shinji 
Published: February 2020

Since the reports on self-organized tubular oxide layers on Ti and its alloys by Assefpour-Dezfuly et al[1] and Zwilling et al[2,3], TiO2 nanotube layers have been widely studied in several application fields owing to its unique chemical and physical properties. It was reported that the morphology of the oxide layers is strongly influenced by anodization parameters such as electrolytic composition, applied voltage and electrolyte temperature. However, among the many anodization parameters, the influence of titanium substrate on oxide layer growth has not been clear yet. In the present study, the growth behavior of nanotubular oxide layers was examined by using Ti substrates with various microstructures.
As-received Ti sheets (purity: 99.5%) were heat-treated at 500 °C for 12 h to ensure homogeneity. After the homogenization, some Ti sheets were heat-treated at various temperatures in argon atmosphere. Also, the other sheets were subjected to ARB (Accumulative Roll Bonding) process up to 6 cycles to change the microstructures. Anodization was carried out at 50 V for 3 h in ethylene glycol containing 2 wt% H2O and 0.05 M NH4F. After the anodization, the morphology of oxide layers was characterized by FE-SEM.
Nanotubebular oxide layers were formed on all Ti sheets whereas the growth of nanotubular oxide layer was affected by the microstructure of Ti substrate that can be controlled by heat treatment and ARB process. The grain size increased with increasing heat-treatment temperature, duration while increasing the number of ARB cycle decreased the grain size. Consequentially, nanotubular oxide layer thickness increased with decreasing grain size. Therefore, it was found that the growth behavior may be affected by the numerous lattice defects in substrate introduced by heat-treatment and ARB process.
References
[1] M. Assefpour-Dezfuly, C. Vlachos, E. H. Andrews. Journal of materials science (1984): 3626-3639.
[2] V. Zwilling, E. Darque-Ceretti, A. Boutry-Forveille, D. David, M. Y. Perrin1 and M. Aucouturier. Surface and Interface Analysis (1999): 629-637.
[3] V. Zwilling M. Aucouturier, E. Darque-Ceretti. Electrochimica Acta, (1999): 921-929.
Electroless Plating of Pla and Petg for 3D Printed Flexible Substrates
Authors: Bernasconi Roberto , Natale Gabriele , Levi Marinella , Magagnin Luca 
Published: February 2020

The FDM (fused deposition modelling) 3D printing technology has acquired increasing commercial importance in the last few years. Large scale manufactured devices are nowadays available at low cost and are able to reach performances similar to industrial prototyping machines. Considering this recent new technological evolution, the surface finishing researcher is invited to develop and optimize treatments suitable for tridimensional complex objects made with different polymeric materials. One of the most used polymers for FDM printing is PLA (polylactic acid) due to its dimensional stabily after cooling, a condition needed to avoid deformations during the printing process. PLA presents other desirable properties like biodegradability and good mechanical properties, as well as remarkable disadvantages like poor resistance to aggressive environments and low glass transition temperature. Recently PLA is being replaced in many 3D printing processes by PETG (polyethylene terephthalate glycol-modified), a polymer able to compensate the drawbacks of PLA (with the only main disadvantage of being not biodegradable). An important surface treatment that the objects printed with these two polymers may require is metallization, a process able to make conductive the surface and to give new functional and aesthetic properties to the polymer. Metallization of non-conductive materials can be achieved using techniques like PVD, but one of the most economical is electroless plating.
Starting from this consideration, the present work aims at testing the possibility of electroless NiP and Cu plating on PLA and PETG. The resulting films can be used as deposited or as adhesion layers for the deposition of other metals like decorative chromium. A convenient preparation of the surface must be performed in order to achieve good uniformity and cohesion with the polymeric substrate. Two etching processes, alkaline and acidic, are used to increase the roughness of the surface and permit a good adhesion of the electroless plated metals. The characterization of the pretreatment is therefore presented together with the activation process and the description of the properties of the coatings obtained. To conclude the work and to provide a future perspective the deposition on 3D printed prototypes is performed.
(Invited) Solution-Processing Routes to Conductive Ultrathin Films of Ruthenium Dioxide...on Any Substrate
Authors: Rolison Debra R. , Pala Irina R. , Donakowski Martin D. , Chervin Christopher N. , Long Jeffrey W. , Stroud Rhonda , Brintlinger Todd , Liu Xiao 
Published: February 2020

The deposition of continuous, ultrathin, conductive films from liquid-phase is still a rare processing outcome. We have demonstrated that RuO2 can be deposited from chilled, nonaqueous solutions of RuO4 as an ~10 nm–thick film on planar substrates using a scalable, atom-efficient, self-limiting synthetic protocol [1]. The versatility of this protocol is exemplified in that deposition ensues on any type of substrate—metal, semiconductor, ceramic, polymer, or salt—or whether the substrate is planar, curved, or non-line-of-sight [1–3]. The resulting air- and water-stable conductive oxide, even though nanoscopic, is electrically conductive and broadband transparent over an uncommonly wide range for an oxide—from UV to microwave—far surpassing the spectral window of indium-doped tin oxide (ITO) [1]. Recently, we were able to isolate square centimeters of self-supporting, ultrathin RuO2 films, by releasing them from soluble substrates. The freestanding films are also conductive and transparent, exhibiting unexpected mechanical flexibility and strength. They can then be manipulated and further characterized by being placed on holders (i.e., TEM grids) or devices (i.e. nanofabricated stages for mechanical or thermal transport measurements). We will provide an overview of the synthetic methods and the characterization of this ultrathin, disordered material, including optical, structural, thermal and mechanical properties.
[1] D.R. Rolison, J.W. Long, C.N. Chervin, J.C. Lytle, and K.A. Pettigrew, U.S. Patent #8,889,257; J.W. Long, J.C. Owrutsky, C.N. Chervin, D.R. Rolison, J.S. Melinger, U.S. Patent, issued 9-Dec-2014.
[2] C.N. Chervin, A.M. Lubers, K.A. Pettigrew, J.W. Long, M.A. Westgate, J.J. Fontanella, D.R. Rolison, Nano Lett.
9 (2009) 2316–2321.
[3] C.P. Rhodes, J.W. Long, K.A. Pettigrew, R.M. Stroud, and D.R. Rolison, Nanoscale
3 (2011) 1731–1740.
In Situ Vibrational Spectroscopy of Electrode Interfaces
Authors: Baldelli Steven 
Published: February 2020

In situ sum frequency generation (SFG) vibrational spectroscopy is used to study the alkanethiolate monolayer on metal electrodes. The electrode potential is swept from the double layer region toward the cathodic limits in basic electrolyte solution and the reductive desorption process is observed. Correlations in the cathodic current and SFG spectra are made to help elucidate details of the monolayer film under the desorption process. SFG spectroscopy of the monolayer reveals feature that could not easily be deduced by ex situ analysis.
Superconformal Film Growth: Insights Provided By Seiras
Authors: Moffat Thomas P. , Liu Guokun , Zou Shouzhong , Ou Yang Liang-Yueh , Josell Daniel , Lee Chang Hwa , Richter Lee 
Published: February 2020

State of the art manufacturing of semiconductor devices involves electrodeposition of copper for device wiring and more recently for through-silicon-vias (TSVs). The process depends on the use of electrolyte additives that affect the local deposition rate thereby resulting in superconformal, or bottom–up “superfilling” of trenches and vias. In the case of Damascene processing of submicron features the deposition process is explained by the recently developed curvature enhanced accelerator coverage (CEAC) mechanism. The model stipulates that 1.) the growth velocity is proportional to the local accelerator, or catalyst, surface coverage and 2.) the catalyst remains segregated at the metal/electrolyte interface during copper deposition. For growth on non-planar geometries this leads to enrichment of the catalyst on advancing concave surfaces and dilution on advancing convex sections; thereby giving rise to bottom-up superfilling of recessed surface features such as trenches and vias. In the case of larger features other avenues for feature filling become available that will be outlined in some detail. Despite the success of these superconformal growth processes much remains to be known concerning the detailed molecular nature of the competitive co-adsorption processes involved in both the suppression and acceleration of the metal deposition reaction. The application of in situ surface science tools such as in situ STM and SEIRAS towards a better understanding of the additive interactions will also be detailed. The interaction between adsorbed anions, polyether suppressors, sulfonate terminated thiol/disulfide accelerator additves and water at the growing interface reveal the critical role of hydrophobic/hydrophilic interactions in controlling the growth velocity during metal deposition. The talk will conclude with an overview of the current understanding of additive adsorption, consumption and/or deactivation dynamics relevant to superfilling and microstructural evolution in both Damascene and TSV Cu processing.