Publication practices during the COVID-19 pandemic: Expedited publishing or simply an early bird effect?

This study explores the evolution of publication practices associated with the SARS-CoV-2 research papers, namely, peer-reviewed journal and review articles indexed in PubMed and their associated preprints posted on bioRxiv and medRxiv servers: a total of 4,031 journal article-preprint pairs. Our assessment of various publication delays during the January 2020 to March 2021 period revealed the early bird effect that lies beyond the involvement of any publisher policy action and is directly linked to the emerging nature of new and 'hot' scientific topics. We found that when the early bird effect and data incompleteness are taken into account, COVID-19 related research papers show only a moderately expedited speed of dissemination as compared with the pre-pandemic era. Medians for peer-review and production stage delays were 66 and 15 days, respectively, and the entire conversion process from a preprint to its peer-reviewed journal article version took 109.5 days. The early bird effect produced an ephemeral perception of a global rush in scientific publishing during the early days of the coronavirus pandemic. We emphasize the importance of considering the early bird effect in interpreting publication data collected at the outset of a newly emerging event.

Structure and Properties of Sodium Enneaborate, Na2[B8O11(OH)4]·B(OH)3·2H2O.

Millions of tons of sodium borates are used annually by global industries in diverse applications important to modern society. The Na2O-B2O3-H2O phase diagram in the 0-100 °C temperature range contains 13 unique hydrated crystalline sodium borates, including five important industrial products. Structures were previously reported for each of these except for that having the highest boron content, known as sodium enneaborate, Na4B18O29·11H2O or 2Na2O·9B2O3·11H2O (1). Here we report the single-crystal structure of 1, revealing the structural formula Na2[B8O11(OH)4]·B(OH)3·2H2O, and describe some of its properties and relationships to other sodium borates. The structure of 1 features linear polyborate chains composed of the repeating [B8O11(OH)4]2- fundamental building blocks with interstitial water and boric acid molecules integrated by extensive H bonding. Interstitial sodium cations occur in groups of four with interatomic distances of 3.7830(6) and 3.7932(8) Å. Upon heating, 1 initially becomes amorphous and then crystallizes as α-Na2B8O13 along with amorphous B2O3. Notably, α-Na2B8O13 contains octaborate fundamental building blocks that are topologically equivalent to those in 1. Compound 1 crystallizes in the monoclinic space group P21/n with a = 10.2130(8) Å, b = 12.940(1) Å, c = 12.457(1) Å, ß = 93.070(2)°, V = 1644.0(2) Å3, and Z = 2.

Solid-State Synthesis and Structure of the Enigmatic Ammonium Octaborate: (NH4)2[B7O9(OH)5]·3/4B(OH)3·5/4H2O.

The compound known since the 19th century as ammonium octaborate was structurally characterized revealing the ammonium salt of the ribbon isomer of the heptaborate anion, [B7O9(OH)5](2-), with boric acid and water molecules. Of composition (NH4)2B7.75O12.63·4.88H2O, it approximates the classical ammonium octaborate composition (NH4)2B8O13·6H2O and has the structural formula {(NH4)2[B7O9(OH)5]}4·3B(OH)3·5H2O. It spontaneously forms at room temperature in solid-state mixtures of ammonium tetraborate and ammonium pentaborate. It crystallizes in the monoclinic space group P21/c with a = 11.4137(2) Å, b = 11.8877(2) Å, c = 23.4459(3) Å, ß = 90.092(1)°, V = 3181.19(8) Å(3), and Z = 2 and contains well-ordered ammonium cations and [B7O9(OH)5](2-) anions and disordered B(OH)3 and H2O molecules linked by extensive H bonding. Expeditious solid-state formation of the heptaborate anion under ambient conditions has important implications for development of practical syntheses of industrially useful borates.

An Efficient Halogen-Free Electrolyte for Use in Rechargeable Magnesium Batteries.

Unlocking the full potential of rechargeable magnesium batteries has been partially hindered by the reliance on chloride-based complex systems. Despite the high anodic stability of these electrolytes, they are corrosive toward metallic battery components, which reduce their practical electrochemical window. Following on our new design concept involving boron cluster anions, monocarborane CB11H12(-) produced the first halogen-free, simple-type Mg salt that is compatible with Mg metal and displays an oxidative stability surpassing that of ether solvents. Owing to its inertness and non-corrosive nature, the Mg(CB11H12)2/tetraglyme (MMC/G4) electrolyte system permits standardized methods of high-voltage cathode testing that uses a typical coin cell. This achievement is a turning point in the research and development of Mg electrolytes that has deep implications on realizing practical rechargeable Mg batteries.

Novel synthetic approach to charge-compensated phosphonio-nido-carboranes. Synthesis and structural characterization of neutral mono and bis(phosphonio) nido-ortho-carboranes.

A number of monosubstituted n-(triphenylphosphonio)-7,8-dicarba-nido-undecaboranes (2a, n = 1; 2b, n = 3; 2c, n = 5; 2d, n = 9) were prepared via a cross-coupling reaction between the tetrabutylammonium iodo-7,8-dicarba-nido-undecaborates (1a-d) and PPh3 in the presence of a Pd(PPh3)4 catalyst. The substitution rate was found to depend on the iodine position in the carborane cage. Under similar conditions, the reaction of 5,6-diiodo- (3) and 9,11-diiodo-7,8-dicarba-nido-undecaborate (5) anions exclusively yielded the monosubstitution products 5-iodo-6-(triphenylphosphonio)-7,8-dicarba-nido-undecaborane (4) and 9-iodo-11-(triphenylphosphonio)-7,8-dicarba-nido-undecaborane (6), respectively. The reaction of tetrabutylammonium 6,9-diiodo-7,8-dicarba-nido-undecaborate (7) exclusively produced the phosphine substitution product in the open face of the nido-carborane, 6-iodo-9-triphenylphosphonio-7,8-dicarba-nido-undecaborane (8). The addition of a base (Cs2CO3, NaH) to the reactions of 3 and 5 with PPh3 afforded the corresponding bis(triphenylphosphonio)-7,8-dicarba-nido-undecaboranes, 9 and 10. Compound 10 was also prepared from 6 using the general procedure. The reaction of the triiodocarborane tetrabutylammonium 5,6,9-triiodo-7,8-dicarba-nido-undecaborate (11) with excess PPh3 in the presence of Cs2CO3 and Pd(PPh3)4 only produced neutral 5-iodo-6,9-bis(triphenylphosphonio)-7,8-dicarba-nido-undecaborane (12); no positively charged tris(phosphonio) species formed. The compositions of all prepared compounds were determined by multinuclear NMR spectroscopy and high-resolution mass spectrometry. The structures of compounds 2c, 6, 8, 9, and 12 were established by the X-ray diffraction analysis of single crystals.

Carborane-derived local anesthetics are isomer dependent.

Clinically there is a need for local anesthetics with a greater specificity of action on target cells and longer duration. We have synthesized a series of local anesthetic derivatives we call boronicaines in which the aromatic phenyl ring of lidocaine was replaced with ortho-, meta-, C,C'-dimethyl meta- and para-carborane clusters. The boronicaine derivatives were tested for their analgesic activity and compared with lidocaine using standard procedures in mice following a plantar injection. The compounds differed in their analgesic activity in the following order: ortho-carborane = C,C'-dimethyl meta-carborane > para-carborane > lidocaine > meta-carborane derivative. Both ortho-boronicaine and C,C'-dimethyl meta-boronicaine had longer durations of analgesia than lidocaine. Differences in analgesic efficacies are rationalized by variations in chemical structure and protein binding characteristics.

Direct observation of bis(dicarbollyl)nickel conformers in solution by fluorescence spectroscopy: an approach to redox-controlled metallacarborane molecular motors.

As a continuation of work on metallacarborane-based molecular motors, the structures of substituted bis(dicarbollyl)nickel complexes in Ni(III) and Ni(IV) oxidation states were investigated in solution by fluorescence spectroscopy. Symmetrically positioned cage-linked pyrene molecules served as fluorescent probes to enable the observation of mixed meso-trans/dl-gauche (pyrene monomer fluorescence) and dl-cis/dl-gauche (intramolecular pyrene excimer fluorescence with residual monomer fluorescence) cage conformations of the nickelacarboranes in the Ni(III) and Ni(IV) oxidation states, respectively. The absence of energetically disfavored conformers in solution--dl-cis in the case of nickel(III) complexes and meso-trans in the case of nickel(IV)--was demonstrated based on spectroscopic data and conformer energy calculations in solution. The conformational persistence observed in solution indicates that bis(dicarbollyl)nickel complexes may provide attractive templates for building electrically driven and/or photodriven molecular motors.

An unsolvated buckycatcher and its first dianion.

The X-ray crystallographic study of C60H28 consisting of two tethered corannulene bowls revealed a unique solid-state packing based on tight convex-concave π-π interactions. The controlled reduction of C60H28 resulted in the isolation and structural characterization of its dianion in the form of the rubidium salt that shows an entrapment of counterions by an anionic pincer.

Synthesis of closo- and nido-biscarboranes with rigid unsaturated linkers as precursors to linear metallacarborane-based molecular rods.

Several biscarborane-type derivatives of 8-iodo-1,2-dicarba-closo-dodecaborane (1), suitable as the precursors of linear metallacarborane-based molecular rods, were prepared. The synthesized closo-compounds contained two carborane moieties connected through a rigid linear unsaturated linker. The linkers were based on ethynylene and para-phenylene fragments and their combinations. The deboronation of all reported closo-compounds was selective and afforded nido-products with open pentagonal faces on opposite sides of the molecule, parallel to each other and perpendicular to the main molecular axis. All of the closo and nido products were characterized by a variety of physical methods (NMR, HRMS, IR). The structures of closo-carboranes 3, 6, 9, and 14 and nido-carboranes 15 and 17 were established by X-ray diffraction.

Synthesis of [closo-B12(OH)11NH3]-: a new heterobifunctional dodecaborane scaffold for drug delivery applications.

Effective utilization of [closo-B12H12](2-) derivatives in targeted drug delivery applications depends upon an efficient strategy to differentiate at least one of the 12 vertices on the B12(2-) core. Precursor molecules must also be able to withstand the initial harsh hydrogen peroxide treatment necessary for hydroxylation of the B-H vertices. We report here a method for preparation of the ammonio derivative [closo-B12(OH)11NH3](-) and also demonstrate its utility in construction of a targeted drug delivery scaffold. Treatment of the precursor [closo-B12H11NH3](-) with hydrogen peroxide gives the corresponding nitro derivative [closo-B12(OH)11NO2](2-) in good yield. The nitro group is easily reduced with hydrogen over a Raney nickel catalyst to produce [closo-B12(OH)11NH3](-). The 11 hydroxyl groups can then be readily converted to carbonates or carbamates. As a proof-of-principle of its utility as a drug delivery system, we used the resulting vertex-differentiated ammonio derivative to construct a platinated pro-drug possessing 11 copies of a carboplatin analogue conjugated to the B12(2-) core via carbamate linkage and a fluorescein molecule attached at the remaining vertex by an amide linkage. In vitro cytotoxicity assays demonstrated that activity of an untagged analog was similar to carboplatin against platinum-sensitive A459 cells and higher than carboplatin against platinum-resistant SK-OV-3 cells. Further fluorescence microscopy revealed that the fluorescein-tagged pro-drug localizes to the nuclei of A459 cells.

Acid-induced opening of [closo-B10H10]2- as a new route to 6-substituted nido-B10H13 decaboranes and related carboranes.

Protonation of the polyhedral anion [closo-B(10)H(10)](2-) under superacidic conditions apparently generates an electrophilic intermediate, [B(10)H(13)](+), that forms 6-R-nido-B(10)H(13) (R = aryl, alkyl, triflate) derivatives by electrophilic aromatic substitution, C-H bond activation, or ion-pair collapse, respectively. The proposed mechanism of formation of the 6-R-nido-B(10)H(13) derivatives via the boranocation [B(10)H(13)](+) is discussed. The synthesis of carboranes, starting from 6-R-nido-B(10)H(13) decaboranes, and single-crystal X-ray diffraction analyses of several 6-R-nido-B(10)H(13) decaboranes and carboranes are described.

Carboranes increase the potency of small molecule inhibitors of nicotinamide phosphoribosyltranferase.

Herein we report the use of carboranes to significantly increase the potency of small molecule inhibitors of nicotinamide phosphoribosyltranferase (Nampt), an enzyme that is central to metabolism and cell survival. We compare the inclusion of carborane with other similarly sized substituents and demonstrate that, compared with their purely organic counterparts, these molecules exhibit up to 10-fold greater antiproliferative activity against cancer cells in vitro and a 100-fold increase in Nampt inhibition.

Unfairly forgotten member of the iodocarborane family: synthesis and structural characterization of 8-iodo-1,2-dicarba-closo-dodecaborane, its precursors, and derivatives.

8-Iodo-1,2-dicarba-closo-dodecaborane (7) was prepared in three steps starting from decaborane-14 with 20% overall yield. In the presence of nucleophiles, compound 7 undergoes selective removal of the boron vertex in the position para to the iodine substituent to form the anionic nido-carborane 1-iodo-7,8-dicarba-nido-undecaborate. Capping of the corresponding dicarbollide dianion with BI(3) led to formation of the new carborane, 3,10-diiodo-1,2-dicarba-closo-dodecaborane (15). The same dicarbollide dianion reacts with cobalt and nickel acetylacetonates in anhydrous tetrahydrofuran to form the corresponding bis(dicarbollide) complexes with excellent yields. All compounds were characterized by multinuclear NMR and high-resolution mass spectroscopy. Structures of 2-iododecaborane (2), 8-iodo-1,2-dicarba-closo-dodecaborane (7), 1-ethoxycarbonyl-8-iodo-1,2-dicarba-closo-dodecaborane (10), cesium 1-iodo-7,8-dicarba-nido-undecaborate (13), 3,10-diiodo-1,2-dicarba-closo-dodecaborane (15), and cesium 3,3'-commo-(10-iodo-1,2-dicarba-3-cobalta-closo-dodecaborane)-(10'-iodo-1',2'-dicarba-3'-cobalta-closo-dodecaborane) (16) were established by X-ray analysis of single crystals.