The Tetracyanopyridinide Dimer Dianion, σ‐[TCNPy]22−

The reaction of 2,3,5,6‐tetracyanopyridine (TCNPy) and Cr(C₆H₆)₂ forms diamagnetic σ‐[TCNPy]₂^2? possessing a 1.572(3) Å intrafragment sp³–sp³ bond. This is in contrast to the structurally related 1,2,4,5‐tetracyanobenzene and 1,2,4,5‐tetracyanopyrazine that form π‐dimer dianions possessing long, multicenter bonds.     

Properties of a new ferroelectric crystal family: MCd(NO2)3 [M=NH4, K,Rb, Cs,Tl]

Single crystals of MCd(NO₂)₃, with M=NH₄, K, Rb, Cs, and Tl, respectively, were grown and investigated by means of optical and dielectric methods. The crystals show rhombohedral symmetry (possible space group R 3) and multi-domain patterns at ambient temperature. The compounds exhibit phase transitions above room-temperature of first (M=K) and second order (M=Rb, Cs, Tl), respectively, into cubic high-temperature phases. Observed dielectric anomalies and hysteresis loops point to ferroelectric properties and suggest a relaxational order-disorder mechanism of the nitrite ions to be responsible for the transitions. The MCd-(NO₂)₃-compounds are seen to represent a new family of ferroelectrics with a cubic prototypic phase closely related to the structural type of the perovskites. The transions are classified by symmetry considerations, and a possible structure of the cubic high-temperature phase with space group Pm3 is proposed.     

2-(2-pyridyl-)ethyl esters A new carboxyl protecting group in peptide synthesis

2-(2-pyridyl-)ethyl esters are used as chemically inert, highly selective protecting groups that are removable under mild conditions via a two step procedure.     

Beiträge zur Chemie der Pyrrolpigmente, 39. Mitt.: Ein Kraftfeldmodell zur konformationsanalytischen Untersuchung von Gallenfarbstoffen

A force field model was designed with respect to the special needs of bile pigments. It is parametrized and tested using partial structures of bile pigments as well as an integral pigment; the solution structures of the molecules were previously deduced using independent experimental methods.

38. Mitt::Falk, H., Schlederer, T., Wolshann, P., Mh. Chem.112, 199 (1981).