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Exchange interactions in bis(diethyldithiocarbamato)copper(II), Cu(detc)2
97. number
Volume
1
CHEMICAL
PHYSICS
LETTERS
6 hfay 1983
EXCHANGE INTERACTIONS IN BIS(DIETHYLDITHIOCARBAMATO)COPPER(II), B.L. RAMAKRISHNA D~~~xrrmmrof Ckmisrr_r. Kc~c~%cd 13 December
Cu(detc)z
and P-T. MANOHAIUN indion
Irmintre of Technology, fifadras600 036. Indln
1982: in final form 23 February
1983
Tlx c\ch.ange coupling constant J in bis(diethyldithiourbamato)copper (II) has been derived through analysis of the i_PK g wluc~ and linewidth as J function of orientation, frequency and temperature. The single line in the ac*_hne is due to the a\er.@tz of the tine-structure splitting by interdimer exchange for which D lower limit of 0.02 cm has been obr~inrd. .Anai)sic of the spectra in the br plane gives an estimate of 0.008 cm-’ for the intersite exchxqe.
1. Introduction
‘There has been extensive work done on the magnetic propcrtics of bis(dialkyldithiocarbamato)copper(I1) con~ple-xcs.
Of these
c~rb~ol~to)copper(II)
con~pounds.
bis(diethyldithio-
has received much attention
[ I- I2 J. Cu(detc)z crystallircs in the PZt /C space group \I]_ The structure consists of a pair of squareplaudr Cu(dstc)l units linked Into a dirner by coordiration of one in-plme sulfur in an out-of-plane site of the Jdjaccnt copper ion. Copper is in a tetragoond pyranklA envirmmcnt with four short in-plane Cu-S bonds dt 1.3 x .md one out-of-plane bond at a distance 2.X5 ,A. The Cu -S-Cu angle is 86.9”. The sixth coordin.ttiou site of copper is occupied by a hydrogen atom f~tmr JII ethyl goup of a neighbouring dimer. The interdmcr interactions are not as strong, the two nearest mgnetiwlly incquivalent sites being 9.5 A apart and .~long rile chain the interdimer distance is 6.0 A. In fig. 1 the proicction of Cu(delc), down the “b” axis sho\\s rllc suCccssive dimers up “2. (taken from ref. IS]). l’.m.un+nrtic anisotropy mcasurernents [2) yielded iI ne.!rly rsorropif cxllJ11ge coupling with J,, = 8 cm-* anti JL = 6.6 in--* . The magnetic susceptibility measureIncuts 13.41 could be tit lo the modified van Vleck zqlIJriuI1
Fig. 1_ Rojcction of C~(detc)~ the successive dimers up ‘0”.
0 009-2614/83/0000-0000/S
down the ‘b” axis showing
03.00 0 1983 North-Holland
CHEMICAL PHYSICS LETTERS
Volume 97, number 1
6%
5b2
w
6 hkiy 1983
Fig. 3. Contour diigram of the three n-type MOs of 1.2.3-triaziie (1) calculated by the HAM/3 method. The interval between the contour values is 0.04. Full and dashed lines distinguish between amplitudes of different sign. nodes are indicated by short dashes.
lated and observed ionization energies, the assignment of the first five PE bands of 1 seems unproblematic.
Acknowledgement
The only question concerns the ordering of the 2bl(rr) and la?(n) levels which are predicted to be neardegen-
We are grateful to the Fonds der Chemischen Industrie and the BASF Aktiengesellschaft in LudwiSshafen for financial Support.
erate
by the theoretical
procedures
(part
of the observ-
ed splitting of bands 3 and 4 may be of pseudo-JahnTeller origin)_ However, the large shift of band 3 relative to the small shift of band 4 on methyl substitution in the S-position is only consistent with assignment of band 3 to the 2bl(rr) and band 4 to the la2(rr) level. This follows from the different amplitudes of the corresponding MOs in this position (fig. 2). The excellent performance of the naive HMO model is remarkable, particularly in the case of the problematic II levels. Not only is the actual shape of the n-type MOs (e.g. fig. 3) much more complicated than indicated by the simple “lone-pair” combinations $I~, $2 and rj3, but also serious breakdown of Koopmans’ approximation has been predicted for the azines [9] _ Nevertheless, experience has shown that all significant effects can effectively be absorbed into empirical parameters such asA,,‘% orIho93c mem,“ndqp, [1,2,3J-It should further be noted that the obvious similarity of the PE spectra of 1 and 1,3,5triazine [l] is easily understandable in terms of the HMO model (section
3).
5 _Experimental The compounds
1
to 6 were prepared according to [lo] - The PE spectra were recorded at room temperature on a PS lS instrument (Perkin-Elmer Ltd_, Beaconsfield, UK).
directions
References [I] R. Gieiter, E. Heilbronner and V. Homuns. Helv. Chim. Acta 55 (1972) 255 121 R. Gleiter. _M_Kobayashi, H. Neunhoeffer and J. SpangetLarsen, Chem Phyr Letters 46 (1977) 731. 13) T. Koopmans, Physica 1 (1934) 104. [4] F_ Brogli, E. Hetibronner and T_ Kobayashi. Helv. chim. Acta 55 (1972) 174. IS] J_ Spanset-Larsen, J. Electron Spectsy. 2 (1973) 33; 3 (1974) 369; QCPE ll(l974) 246. [6] J. Linderberg and Y. &a. Propagators in quantum chemistr_v (Academic Press, New York, 1973) p_ 82; J. Linderberg, Y. 6hm and P-W_ Thulstrup, ix Quantum science - methods and structure (Plenum Press. New York, 1976) p. 93. (71 I_ Asbrink. C_ Fridb. E Lindhohn. S. de Bruijn and D_P_ Chong. Pbysica scripta 39 (1980) 475; L. Asbrink, C. Fridh and E. Lindholm, QCPE 12 (19SO) 393_ [ 8 J M.H. Palmer, A-J. GaskeB and R-H. FindJay, 1. Chem. Sot. Perkin II (1974) 778. [9] W. van Niessen, W-P_ Kraemer and G-H-F_ Diercksen, Chem Phys. 41(1979) 113. [IO] A. Ohsawa, H. Arai. H. Onishi and H. Igeta, J. Chem. Sot. Chem. Commun. (1980) 1182; (1981) 1174; hl. Clausen, Ph.D. Thesis, TH Darmstadt.
in the literature
97
Volume
1
CHEMICAL
PHYSICS
LETTERS
6 hfay 1983
EXCHANGE INTERACTIONS IN BIS(DIETHYLDITHIOCARBAMATO)COPPER(II), B.L. RAMAKRISHNA D~~~xrrmmrof Ckmisrr_r. Kc~c~%cd 13 December
Cu(detc)z
and P-T. MANOHAIUN indion
Irmintre of Technology, fifadras600 036. Indln
1982: in final form 23 February
1983
Tlx c\ch.ange coupling constant J in bis(diethyldithiourbamato)copper (II) has been derived through analysis of the i_PK g wluc~ and linewidth as J function of orientation, frequency and temperature. The single line in the ac*_hne is due to the a\er.@tz of the tine-structure splitting by interdimer exchange for which D lower limit of 0.02 cm has been obr~inrd. .Anai)sic of the spectra in the br plane gives an estimate of 0.008 cm-’ for the intersite exchxqe.
1. Introduction
‘There has been extensive work done on the magnetic propcrtics of bis(dialkyldithiocarbamato)copper(I1) con~ple-xcs.
Of these
c~rb~ol~to)copper(II)
con~pounds.
bis(diethyldithio-
has received much attention
[ I- I2 J. Cu(detc)z crystallircs in the PZt /C space group \I]_ The structure consists of a pair of squareplaudr Cu(dstc)l units linked Into a dirner by coordiration of one in-plme sulfur in an out-of-plane site of the Jdjaccnt copper ion. Copper is in a tetragoond pyranklA envirmmcnt with four short in-plane Cu-S bonds dt 1.3 x .md one out-of-plane bond at a distance 2.X5 ,A. The Cu -S-Cu angle is 86.9”. The sixth coordin.ttiou site of copper is occupied by a hydrogen atom f~tmr JII ethyl goup of a neighbouring dimer. The interdmcr interactions are not as strong, the two nearest mgnetiwlly incquivalent sites being 9.5 A apart and .~long rile chain the interdimer distance is 6.0 A. In fig. 1 the proicction of Cu(delc), down the “b” axis sho\\s rllc suCccssive dimers up “2. (taken from ref. IS]). l’.m.un+nrtic anisotropy mcasurernents [2) yielded iI ne.!rly rsorropif cxllJ11ge coupling with J,, = 8 cm-* anti JL = 6.6 in--* . The magnetic susceptibility measureIncuts 13.41 could be tit lo the modified van Vleck zqlIJriuI1
Fig. 1_ Rojcction of C~(detc)~ the successive dimers up ‘0”.
0 009-2614/83/0000-0000/S
down the ‘b” axis showing
03.00 0 1983 North-Holland
CHEMICAL PHYSICS LETTERS
Volume 97, number 1
6%
5b2
w
6 hkiy 1983
Fig. 3. Contour diigram of the three n-type MOs of 1.2.3-triaziie (1) calculated by the HAM/3 method. The interval between the contour values is 0.04. Full and dashed lines distinguish between amplitudes of different sign. nodes are indicated by short dashes.
lated and observed ionization energies, the assignment of the first five PE bands of 1 seems unproblematic.
Acknowledgement
The only question concerns the ordering of the 2bl(rr) and la?(n) levels which are predicted to be neardegen-
We are grateful to the Fonds der Chemischen Industrie and the BASF Aktiengesellschaft in LudwiSshafen for financial Support.
erate
by the theoretical
procedures
(part
of the observ-
ed splitting of bands 3 and 4 may be of pseudo-JahnTeller origin)_ However, the large shift of band 3 relative to the small shift of band 4 on methyl substitution in the S-position is only consistent with assignment of band 3 to the 2bl(rr) and band 4 to the la2(rr) level. This follows from the different amplitudes of the corresponding MOs in this position (fig. 2). The excellent performance of the naive HMO model is remarkable, particularly in the case of the problematic II levels. Not only is the actual shape of the n-type MOs (e.g. fig. 3) much more complicated than indicated by the simple “lone-pair” combinations $I~, $2 and rj3, but also serious breakdown of Koopmans’ approximation has been predicted for the azines [9] _ Nevertheless, experience has shown that all significant effects can effectively be absorbed into empirical parameters such asA,,‘% orIho93c mem,“ndqp, [1,2,3J-It should further be noted that the obvious similarity of the PE spectra of 1 and 1,3,5triazine [l] is easily understandable in terms of the HMO model (section
3).
5 _Experimental The compounds
1
to 6 were prepared according to [lo] - The PE spectra were recorded at room temperature on a PS lS instrument (Perkin-Elmer Ltd_, Beaconsfield, UK).
directions
References [I] R. Gieiter, E. Heilbronner and V. Homuns. Helv. Chim. Acta 55 (1972) 255 121 R. Gleiter. _M_Kobayashi, H. Neunhoeffer and J. SpangetLarsen, Chem Phyr Letters 46 (1977) 731. 13) T. Koopmans, Physica 1 (1934) 104. [4] F_ Brogli, E. Hetibronner and T_ Kobayashi. Helv. chim. Acta 55 (1972) 174. IS] J_ Spanset-Larsen, J. Electron Spectsy. 2 (1973) 33; 3 (1974) 369; QCPE ll(l974) 246. [6] J. Linderberg and Y. &a. Propagators in quantum chemistr_v (Academic Press, New York, 1973) p_ 82; J. Linderberg, Y. 6hm and P-W_ Thulstrup, ix Quantum science - methods and structure (Plenum Press. New York, 1976) p. 93. (71 I_ Asbrink. C_ Fridb. E Lindhohn. S. de Bruijn and D_P_ Chong. Pbysica scripta 39 (1980) 475; L. Asbrink, C. Fridh and E. Lindholm, QCPE 12 (19SO) 393_ [ 8 J M.H. Palmer, A-J. GaskeB and R-H. FindJay, 1. Chem. Sot. Perkin II (1974) 778. [9] W. van Niessen, W-P_ Kraemer and G-H-F_ Diercksen, Chem Phys. 41(1979) 113. [IO] A. Ohsawa, H. Arai. H. Onishi and H. Igeta, J. Chem. Sot. Chem. Commun. (1980) 1182; (1981) 1174; hl. Clausen, Ph.D. Thesis, TH Darmstadt.
in the literature
97