Hans Peter Jensen

DifferentiaI PoIarization Spectroscopy on Single Crystals of Transition Metal Complexes

Abstract In the last decade there has been a growing interest in phase modulation spectroscopy of general anisotropic media due to the fact that the piezoelectric (photoelastic) modulator, described in 1969 by Kemp [1], features the possibility of changing a spectrophotometer from the “circular dichroism mode” (CD) into the “linear dichroism mode” (LD) without any alterations in the lightpath, but only through a change of the electronic system composing the spectrophotometer [2–4]. This contrasts with situations in which a Pockels cell is used as the modulator [5]. The instrumental set-up of this type of instrument is fixed to such an extent that fairly drastic changes have to be introduced in the optical path in order to convert the machine from a circular into a linear dichrograph [6–8].

Modulated polarization spectroscopy on anisotropic, optically active single crystals

Abstract Conditions in phase modulated spectroscopy on anisotropic single crystals are discussed in the light of recent investigations of crystal circular dichroisms.

Molecular structure of Schiff bases and their transition metal ion complexes, Part XIX. [N,N′-1,2-propanebis(pyrrol-2-yl-methyleneaminato)]-copper(II) and [N,N′-1,2-propanebis(pyrrol-2-acetyl-methyleneaminato)]-copper(II)

SummaryThe structures of dimeric Schiff bases and copper(II) complexes derived from (R)-(-)D-1,2-propanediamine together with pyrrole-2-aldehyde and 2-acetylpyrrole are elucidated by use of circular dichroism spectroscopy, and it is concluded that the complexes are non-planar and of opposite chirality due to 1,3-interactions between substituents on the propylene bridge and the chromophoric units.

Solid State Circular Dichroism Spectra Obtained by Phase Modulation Spectroscopy Exemplified by the Tris(Ethylenediamine)chromium(III) Chromophore

This paper shows what a marvelous thing it is to be able to get a complete dichroic tensor for an absorption band, how useful this information is, and what elegant tools there are available to help one out; namely, polarization, modulation spectroscopy, and group theory.

Condensation products of formylcamphor with diamines : Structures in alcoholic solutions as derived from uv absorption and circular dichroism spectroscopy

Abstract The condensation products of optically active diamines with two molecules of formylcamphor have been investigated in methanolic solutions, where the formylcamphor chromophore is known to exist in the anti or (E) configuration. UV absorption and circular dichroism spectra are rationalised within an exciton formalism to give information about the absolute configuration. As with chloroform solutions, where the chromophore exists in the syn configuration, it is demonstrated that the title compounds may achieve the low energy conformation in seemingly different ways depending on substituents. Because of the different structure of the molecule when the chromophore is in the anti configuration as compared with the syn configuration, rotational conformations with respect to the substituted ethylene bridge in the same compound may be different in CH3OH and CHCl3. Finally “chelating solvation” in hydrogen bonding media is demonstrated through dissolution of the compounds in various alcohols.