Near infrared photolysis of a Ru polypyridyl complex by upconverting nanoparticles

NaYF4:Yb3+/Er3+nanocrystals upconvert near infrared light (980 nm) into higher energy visible photons capable of effecting the photodissociation of the monodentate pyridyl ligand in cis-[Ru(bpy)2(py)2]Cl2: opening an opportunity for advancing the use of photoactivatable metal complexes in medicine and biology

Interchain hydrogen-bonding interactions may facilitate translocation of K(+) ions across the potassium channel selectivity filter, as suggested by synthetic modeling chemistry

A 4-fold symmetric arrangement of TVGYG polypeptides forms the selectivity filter of the K(+) channel from Streptomyces lividans (KcsA). We report the synthesis and properties of synthetic models for the filter, p-tert-butyl-calix[4]arene-(OCH(2)CO-XOBz)(4) (X = V, VG, VGY), 1–3. The first cation (Na(+), K(+)) binds to the four -{OCH(2)CO}- units, a region devised to mimic the metal-binding site formed by the four T residues in KcsA. NMR studies reveal that cations and valine amide protons compete for the carbonyl oxygen atoms, converting N—H(Val)⋅⋅⋅O⩵C hydrogen bonds to M(+)⋅⋅⋅O⩵C bonds (M(+) = Na(+) or K(+)). The strength of these interchain N—H(Val)⋅⋅⋅O⩵C hydrogen bonds varies in the order 3 > 2 > 1. We propose that such interchain H-bonding may destabilize metal binding in the selectivity filter and thus help create the low energy barrier needed for rapid cation translocation

Co-ordinative properties of a tripodal trisamide ligand with a capped octahedral preference

An investigation into the co-ordination chemistry of tris(6-pivaloylamino-2-pyridylmethyl)amine (TPPA) shows a preference for capped octahedral geometry when no additional donors are present. This tripodal ligand yields capped octahedral complexes upon co-ordination to a series of first row transition metals when the counter-ion is a perchlorate, bromide or iodide ion. The exact geometry has been confirmed by shape mapping calculations. The largest variation from the capped octahedral geometry is observed in the case of nickel(II), indicating a greater octahedral preference of this metal ion

Structural chemistry of oximes

Oximes (RR'C=N-OH) represent an important class of organic compounds with a wide range of practical applications, but a systematic examination of the structural chemistry of such compounds has so far not been carried out. Herein, we report a systematic analysis of intermolecular homomeric oxime•••oxime interactions, and identify hydrogen-bond patterns for four major categories of oximes (R' = -H, -CH[subscript 3], -NH[subscript 2], -CN), based on all available structural data in the CSD, complemented by six new relevant crystal structures. The structural behavior of oximes examined here, can be divided into four groups depending on which type of predominant oxime•••oxime interactions they present in the solid-state; (i) O-H•••N dimers (R[superscript 2][subscript 2](6)), (ii) O-H•••N catemers (C(3)), (iii) O-H•••O catemers (C(2)), and (iv) oximes in which the R' group accepts a hydrogen bond from the oxime moiety catemers (C(6)). The electronic and structural effects of the substituent (R') on the resulting assembly has been explored in detail in order to rationalize the connection between molecular structure and supramolecular assembly