PARTIAL QUADRUPOLE SPLITTING OF Fe-57 SPECIES PRODUCED FROM Co-57-LABELLED WERNER COMPLEXES

The quadrupole splittin values of the species produced from 'the 57~o(~~)57~e process were investigated in the various 58Co-labelled Werner-type co-ordination compounds. One of the two components of the decayed species found in the emission Mijssbauer svectra was assigned to high-spin species of Fe(I1) pr_oduced after the EC-decay based on their large quadrupole splittings and isomer shifts. The other component was ascribed to co-ordinated 5 7 ~ e ( ~ ~ ~ ) species, since the quadrupole splittings of the species were well represented by using the partial quadrupole splitting of each ligand. A number of efforts have been devoted to investigate the chemical effect associated with the EC decay process in 7 ~ o (111) co-ordination compounds. It is generally recognized that the high spin 5 7 ~ e (11) species are produced when 5 7 ~ o decays to 5 7 ~ e through the EC decay in the low spin Co(II1) Werner complexes /l/. However, it may also be expected that the low spin Fe(II), low spin Fe(II1) and high spin Fe(II1) species be produced through the process. Bancroft et al. /2/ have studied on the systematics of the quadrupole splitting (QS) of the low spin Fe(I1) Werner complexes and shown that the QS values are given by adopting the concept of the partial quadrupole splitting (PQS) of each ligand. In the present work, the chemical states of 5 7 ~ e species produced from 7 ~ o (111) complexes are examined on the basis of the concept of PQS. 1. Experimental-.57~o-labelled complexes were prepared from solutions containing about 50 mg of Co(I1) and about 0.5 mCi of carrier-free 5 7 ~ o according to the literature 1 3 1 . The source materials were kept in a cryostat at the liquid nitrogen temperature and the emission Gssbauer spectra were measured agains.t an 57~e-enriched stainless steel absorber moving in a constant acceleration mode at room temperature. 2. Results and discussion.The PQS value of a ligand is expressed as follows : PQSL = 112 eQ p/r3 where e is protonic charge; Q, quadrupole moment of nucleus; p, charge density of ligand in point charge model; and r, distance between nucleus and ligand in point charge model. The QS values of MAB5 type-transMA2B4 typeand cis-MAzBt, type-Werner complex can be expected to be 2(PQSA PQSB ), 4(PQSA PQSB) and -2(PQSA PQSB), respectively. The ratio of the magnitude~ of QS of these three complexes is predicted to be 1:2:1. Typical emission Mgssbauer spectra are shown in figure 1. 2 0 2 4 Velocity (mm/s) Fig. 1 : Typical emission Mijssbauer spectra of 5.7~o (111)-Werner CO-ordi ation compounds; a, trans1' 'CO (Non) (NH~)~]NO~; b,Ts7co(~z0) (NHS) 51 (No31 3; c, K~~~~COCL(CN) 51 . 29 Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792151