The Topology of Molecules with Twelve Fused Phenyl Rings ([12]Circulenes): Rings, Infinitenes, and Möbius Infinitenes.

Following the recent preparation of infinitene ( , , 862-871), a computational (ωB97XD/6-311G(d)) exploration of 42 isomeric compounds with 12 fused phenyl rings identified structures with linking number of zero (ring, saddle, and ribbon shapes), two (infinitene-like shape), and one (Möbius infinitene shape) is reported. An infinitene isomer composed of two [5]helicene fragments connected to two stacked phenyl rings and a Möbius infinitene isomer are identified that are more stable than the known infinitene. The energies of the structures are examined by assessing their macrocyclization (strain) energies, π-stacking, and possible aromaticity.

Newly Diagnosed Children with Cancer Have Lower 25-Vitamin D Levels than Their Cancer-Free Peers: A Comparison across Age, Race, and Sex.

Children with cancer have a greater risk for vitamin D concerns because of compromised health before diagnosis, the disease itself, and treatments for the cancer. This IRB-approved retrospective, matched case−control study of children with and without cancer included three race categories: black, other, and Caucasian. This is the first study to directly compare serum 25-hydroxy vitamin D (25(OH)D) levels and status in newly diagnosed pediatric cancer patients with age-, sex-, and race-matched cancer-free children from the same geographic region of the US, all of whom are free from other conditions that negatively impact 25(OH)D levels.

A Comparison of Lumbar Spine and Lateral Distal Femur Bone Density in Girls With Rett Syndrome.

Patients with Rett syndrome (RS) are at risk for low bone mineral density (BMD) and femoral fractures. In patients with RS, assessment with lateral distal femur (LDF) dual-energy X-ray absorptiometry (DXA) is recommended and clinically relevant. This study is the first to assess LDF BMD in girls with RS, and to compare LDF BMD results with lumbar spine BMD results in RS.

Cycloparaphenylene Möbius trefoils.

DFT computations (ωB97X-D/6-31G(d)) of eight different cycloparaphenylenes that have three internal linking groups are shown to have two different conformations that express interesting Möbius topologies. The D conformers have linking numbers Lk of 3 (three half-twists as a trefoil), and the much more stable C conformers have a single half-twist, Lk = 1.

Cycloparaphenylene Lemniscates and Trefoils.

A number of variants of the recently synthesized cycloparaphenylene lemniscates have been explored at ωB97X-D/6-311G(d). Lemniscates with four to eight phenyl rings in each loop having the N-N, C═C, or B-N bond as the linkage all exhibit the figure-eight shape. Their ring strain energies (RSEs) are relatively independent of the nature of the linkage bond, but the RSE does systematically decrease with the increasing size of the loop.

Planar rings in nano-Saturns and related complexes.

Nano-Saturn complexes with a planar horizontal ring can be constructed by selective nitrogen substitution into the ortho-positions in polyaryl macrocycles. A number of intriguing supermolecular complexes can be created with these planar or ribbon macrocycles, including nano-Saturns with a flat ring, nano-Saturns with an encircling belt, and nanotubes encircled by belts or rings. These systems are investigated using DFT (B3LYP-D3/6-31G(d)), which predicts their structures and finds them to have significant binding enthalpies.

Chiral Superbases with Extended Hydrogen Bond Networks.

Extended hydrogen bond networks can substantially increase basicity through stabilization of the resultant conjugate acid. In this study, the chiral superbases (9-11) having anilinyl substituents attached to the prototype superbase 1,8-bis(dimethylamino)naphthalene 1 are examined using DFT methods (PBE1PBE/6-311+G(d,p). While in the gas phase, these are more basic than 1, in THF solution they are slightly weaker bases than 1.

"Planetary Orbit" Systems Composed of Cycloparaphenylenes.

Cycloparaphenylenes (CPP) can serve as both guest and host in a complex. Geometric analysis indicates that optimal binding occurs when the CPP nanohoops differ by five phenyl rings. Employing C-PCM(THF)/ωB97X-D/6-31G(d) computations, we find that the strongest binding does occur when the host and guest differ by five phenyl rings.

Designing a "Flatter" ExBox(4+) Analogue.

Analogues of ExBox(4+) 1 are proposed that possess triaryl fragments that are nearly flat. These two new hosts are predicted by density functional theory (ωB97X-D/6-311G(d,p)) to bind five small linear acenes more tightly than does 1. The "flatter" triaryl fragments provide a less congested interior along with improved π-π-stacking between these hosts and guests.

Cyclooctatetraenophanes: A Computational Study.

DFT (ωB97X-D, B3LYP-D3, M06-2x, and B3LYP) along with MP2 computations were performed on four cyclophanes composed of two or three cyclooctatetraene (COT) rings connected by two, four, or eight ethylene bridges. Both COT rings in cyclophanes with two ethylene bridges (2) and with four bridges in the 1, 2, 5, and 6 positions (6) are in a tub conformation. However, the cyclophane with the four bridges in the 1, 3, 5, and 7 positions (7) is notable for the near planar geometry of the COT rings.

Pamidronate Treatment to Prevent Reoccurring Fractures in Children With Cerebral Palsy.

Background: Some children with cerebral palsy (CP) have frequent fractures due to low bone mineral density and receive treatment with pamidronate, an intravenous bisphosphonate. Our review evaluates the outcome of pamidronate treatment in these children.

Methods: A retrospective chart review was performed, and 32 patients (14 girls and 18 boys) with CP Gross Motor Function Classification System level III (2 patients), IV (3 patients), and V (27 patients) treated with 5 courses of pamidronate for low mineral density were identified.

All-carbon, neutral analogue of ExBox4+: A DFT study of polycyclic aromatic hydrocarbon binding.

To assess the role that electrostatic interactions play in the binding of polycyclic aromatic hydrocarbons within ExBox(4+) 1, we report ωB97X-D/6-311G(d,p) computations of the binding of five small linear acenes with the hydrocarbon neutral analogue 5 in both the gas phase and acetonitrile solution. The terphenyl units of 5 are less bowed outward than are the ExBIPY units of 5, due to the lack of charge repulsion. This manifests in a much smaller ring strain energy in 5 than 1.

Microsolvation of 1,4-butanediol: the competition between intra- and intermolecular hydrogen bonding.

The conformational space of 1,4-butanediol was examined at ωB97X-D/6-311+G(d,p). Of the 65 conformers examined, the seven lowest energy conformations have an internal hydrogen bond. The strength of this hydrogen bond is estimated to be 4 kcal mol(-1).

Conformational equilibria in butane-1,4-diol: a benchmark of a prototypical system with strong intramolecular H-bonds.

Explicitly correlated CCSD(T) valence basis limit relative energies were obtained for the 65 conformers of butane-1,4-diol, a prototypical system with a strong internal hydrogen bond. The performance of a variety of ab initio and DFT methods (with and without empirical dispersion corrections) was assessed in detail. Consideration of all pairwise conformer energies provides a performance gauge for both H-bonds and van der Waals interactions, aside from internal strain of angles and bonds.

Amine superbases stabilized by extended hydrogen bond networks.

Extended hydrogen-bonding networks as a mechanism for creating superbases is explored through six different amine scaffolds: linear acenes, cyclohexane, decalin, triptycene, adamantane, and [2.2]paracyclophane. The gas-phase proton affinities of 21 different potential superbases were computed at the ωB97X-D/6-311+G(2d,p) level.

DFT study of the ExBox·aromatic hydrocarbon host-guest complex.

The structures of ExBox(4+) 1 and its host-guest complexes with the linear acenes benzene, naphthalene, anthracene, and tetracene were optimized using DFT (ωB97X-D/6-311G(d,p)) in both the gas and solution phases. The structure of 1 systematically varies as it moves from the gas to solution to the solid phase: the outward bending of the triaryl fragment diminishes in this series. The structures of the complexes with anthracene and tetracene are in very good agreement with their X-ray structures.

Cerebral palsy patients discovered dead during sleep: experience from a comprehensive tertiary pediatric center.

Objectives: It is not uncommon for children with cerebral palsy (CP) to be discovered dead during sleep (DDDS); however, the factors associated with this pattern of mortality remain unknown. The current study aims to describe the mortality associated with children with CP from a single, tertiary care center who were DDDS.

Methods: A retrospective (case-only) design to examine proportionate mortality and patient characteristics and co-morbidities that may be related to children DDDS between 1993 and 2011.

InChI: a user's perspective.

Exchange of chemical structures between practicing chemists is essential to chemical communication. The International Chemical Identifier (InChI) provides a means for lossless communication of structures without resort to any proprietary software or databases nor does it require any payment or royalty fees. This perspective describes why the InChI is valuable to all chemists and how it will be an essential component of creating the chemical web.

Lower extremity bone mineral density in children with congenital spinal dysfunction.

Aim: To assess lower extremity bone mineral density (BMD) of children with congenital spinal dysfunction and examine factors that may influence BMD in this population.

Method: Forty-four children (25 females, 19 males) aged 6 to 18 years (mean 11 y 11 mo, SD 3 y 6 mo) with congenital spinal dysfunction (35 with myelomeningocele, seven with lipomas, one with sacral agenesis, one with caudal regression) were enrolled in the study. A health survey including ambulatory status, history of bladder augmentation, and history of fracture was administered.

Mechanism of thiolate-disulfide exchange: addition-elimination or effectively S(N)2? Effect of a shallow intermediate in gas-phase direct dynamics simulations.

Direct dynamics trajectory simulations were performed for two examples of the thiolate-disulfide exchange reaction, that is, HS(-) + HSSH and CH(3)S(-) + CH(3)SSCH(3). The trajectories were computed for the PBE0/6-31+G(d) potential energy surface using both classical microcanonical sampling at the ion-dipole complex and quasi-classical Boltzmann sampling (T = 300 K) at the central transition state. The potential energy surface for these reactions involves a hypercoordinate sulfur intermediate.

Extended hydrogen bond network enabled superbases.

New superbases, those organic compounds whose basicities are greater than that of proton sponge, are suggested that involve extended hydrogen-bonding networks. Addition of aminoethyl and related groups to the 1,8-diaminonaphthalene framework provide second- and third-layer hydrogen bonding in the conjugate base. DFT computations predict these compounds to be 10-15 kcal mol(-1) more basic than the proton sponge.

Fracture after bisphosphonate treatment in children with cerebral palsy: the role of stress risers.

Background: In the nonambulatory cerebral palsy (CP) population with a prior history of fracture, the use of pamidronate is not always effective in preventing further fractures.

Objective: To test the hypothesis that when fractures occur after cyclic pamidronate, they will be at the proximal or distal end of a pamidronate band.

Materials And Methods: Retrospective review of our CP patient database revealed 53 children who had received one or more complete courses of pamidronate therapy (five cycles over 12 months).

Microsolvation of uracil and its conjugate bases: a DFT study of the role of solvation on acidity.

The effect of microsolvation on the deprotonation energies of uracil was examined using DFT. The structures of uracil and its N(1) and N(3) conjugate bases were optimized with zero to six associated water molecules. Multiple configurations (upward of 93) of these hydrated clusters were located at PBE1PBE/6-311+G(d,p).

DFT study of [2.2]-, [3.3]-, and [4.4]paracyclophanes: strain energy, conformations, and rotational barriers.

The three smallest symmetrical paracyclophanes, having tethers with two, three, or four methylene groups, have been examined with four density functional methods (B3LYP, M06-2x, B97-D, ωB97X-D). The geometries predicted by functionals accounting for medium-range correlation or long-range exchange and/or dispersion are in close agreement with experiment. In addition, these methods provide similar estimates of the strain energy of the paracylcophanes, which decrease with increasing tether length.

DFT study of cycloparaphenylenes and heteroatom-substituted nanohoops.

Nanohoops are macrocycles formed of aromatic rings linked in a 1,4' fashion. Cycloparaphenylenes 1 and nitrogen analogues formed from the building blocks pyridinyl (2), pyrazinyl (3), pyridazinyl (4), and pyrimidinyl (5) are examined at B3LYP/6-31G(d). The nanohoops contain 3-24 repeat units.