Chemical Science Blog

Scientists in Japan have developed the size-selective syntheses of the four “missing” cycloparaphenylenes (CPP)  ([9], [10], [11] and [13]), which complete the sequence of [6]-[16]CPP. It is important to have access to all of the CPPs in pure form for their future applications and for ring-size effect studies. The synthesis of CPPs was only recently realised (in 2008) and these molecules could find significant utility in supramolecular chemistry and materials science.

Link to journal article
Size-selective synthesis of [9]-[11] and [13]cycloparaphenylenes
Y Ishii et al
Chem. Sci., 2012, DOI: 10.1039/c2sc20343j

Scientists in the US have developed an acylation reagent that can address shortcomings in the acylation of several complex natural products and therapeutics that are widely used in disease treatment and clinical trials. 

The reactions include the inefficient regioselective acylation in rapamycin and paclitaxel and the inefficient acylation of tertiary hydroxyl groups in camptothecin.

Link to journal article
Zinc Complex Mediated Regioselective O-Acylation of Therapeutic Agents
R Tong and J Cheng
Chem. Sci., 2012, DOI: 10.1039/c2sc20239e

Scientists in Canada have used 2D electronic spectroscopy to understand the excitons and charge transfer dynamics (created upon photo excitation) in two conjugated polymers used in organic photovoltaic devices.

The study focuses on the effect of backbone conformation on these properties and the team has found that the weakening of electron-hole correlation controlled by an increasing number of units on the donor and acceptor moieties can lead to higher efficiency of photovoltaic devices by facilitating the charge-transfer process at the heterojunction interfaces.

Although other physical processes should also be taken into account, this study may explain why the photovoltaic devices based not only on the blend of PCDTBT (a popular copolymer for preparing efficient solar cells) and PCBM (an electron acceptor), but also on PCDTBT alone, are efficient.

Link to journal article
Ultrafast relaxation of charge-transfer excitons in low-bandgap conjugated copolymers
I Hwang et al
Chem. Sci., 2012, DOI: 10.1039/c2sc20078c

Scientists in China and Australia have directed the self-assembly of colloidal nanoparticles (NPs) of Au and CdTe into perfect hexagonal microflakes and ultralong microwires, respectively, via stepwise reduction of the electrostatic repulsion potential of neighbouring NPs in the dispersions with the help of L-cysteine.

The work should provide a fundamental basis for better interpretation and prediction of shape-controlled crystallisation and organisation of nanoscale building blocks to mesoscopic and macroscopic artificial solids.

Link to journal article
Shape-Controlled Self-Assembly of Colloidal Nanoparticles
B Zhang, W Zhao and D Wang
Chem. Sci., 2012, DOI: 10.1039/c2sc00016d

Scientists in Germany have prepared gold conjugates with mitochondria-localising peptides. Using these conjugates, the team studied the mechanism of action of gold-based anti-cancer drug candidates.

The team showed that the conjugates were able to break resistance against the commonly used anti-cancer drug cisplatin in p53 mutant cells lines.

Link to journal article
A Spontaneous Gold(I)-Azide Alkyne Cycloaddition Reaction Yields Gold-Peptide Bioconjugates which Overcome Cisplatin Resistance in a p53-Mutant Cancer Cell Line
S D Koster et al
Chem. Sci., 2012, DOI: 10.1039/c2sc01127a

US scientists have used inorganic nodes in metal-organic frameworks (MOFs) as chelating ligand platforms for unusual coordination chemistry; using a MOF’s secondary building units for coordination chemistry is virtually unexplored.

They used the Zn₄O secondary building units of the well known MOF-5 (Zn₄O(1,4-benzenedicarboxylate)₃) as tripodal chelating ligands and kinetically trapped a Ni²⁺ ion in an unusual tetrahedral all-oxygen ligand field. In doing so, they also demonstrated that MOFs can serve as veritable platforms for synthesising inorganic clusters (i.e. a NiZn₃O(carboxylate)₆ unit) that have no analogues in molecular chemistry.

Link to journal article
Lattice-Imposed Geometry in Metal-Organic Frameworks: Lacunary Zn₄O Clusters in MOF-5 Serve as Tripodal Chelating Ligands for Ni²⁺
C K Brozek and M Dinca
Chem. Sci., 2012, DOI: 10.1039/c2sc20306e

Carbon-based drug delivery vehicles such as carbon ‘nano-needles’ have the potential to eliminate the severe side-effects caused by platinum anticancer drugs, but scientists have found it difficult to control the drug’s containment and release. Cisplatin is hydrophilic so trying to contain it within a nanotube’s hydrophobic interior is difficult – the drug readily gets replaced with water. Conversely, strongly hydrophobic-hydrophobic interactions between a drug and the nanotube may prevent the drug’s efficient release.

Scientists from Singapore have trapped a strongly hydrophobic Pt(IV) prodrug in carbon nanotubes and have shown that chemical reduction causes a dramatic reversal in hydrophobicity to release the active Pt(II) complex.

Link to journal article
Platinum(IV) prodrugs entrapped within multiwalled carbon nanotubes: Selective release by chemical reduction and hydrophobicity reversal
J Li et al
Chem. Sci., 2012, DOI: 10.1039/c2sc01086k