Synthesis, structure and properties of new unsymmetrical nickel dithiolene complexes useful as near-infrared dyes

Journal of the Chemical Society, Dalton Transactions

Volumn , Issue 24, 2000, Pages 4639-4644

  Bigoli, Francesco ^c   Cassoux, Patrick ^a   Deplano, Paola ^b   Mercuri, Maria Laura ^a   Pellinghelli, Maria Angela ^b   Pintus, Gloria ^a   Serpe, Angela ^b   Trogu, Emanuele F ^a  

^a UNIVERSITY OF PARMA   (Italy)

^b LCC LABORATOIRE DE CHIMIE DE COORDINATION   (France)

^c UNIVERSITY OF CAGLIARI   (Italy)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0002193564     PISSN: 1470479X     EISSN: None     Source Type: Journal    
DOI: 10.1039/b006206p     Document Type: Article

References (22)

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8. The values at 1400 and 1130 nm have been read directly from the experimental spectra and compared with experimental values obtained for [Ni(PrlJtimdt)J" and [Ni(dmit)2]~. Although a peak deconvolution could have helped in establishing the actual number of peaks and their positions, the results summarised in Fig. 1 strongly indicate that a fast redox equilibrium reaction, shifted to the right, occurs before the transformation of the symmetrical derivatives to the unsymmetrical one: [NiCPrVimdOJ + [Ni(dmit)J2-[Ni(Pr'jtimdt)2]- + [Ni(dmit)J->2 [Ni(PrV timdt)(dmit)]~. This is reflected in the apparent isosbestic points where £([Ni(PrlJtimdt)J-) + £([Ni(dmit)2]-) 2£([Ni(Prl2timdt)(dmit)]"). The symmetrical species, which are equimolar, appear and disappear simultaneously as they are a single species having an apparent £= £([Ni(Prljtimdt)J") + £([Ni(dmit)2]"). No influence of ' the increasingly small amount of the reagents was observed.
9. F. Bigoli, P. Deplano, M.L. Mercuri, M.A. Pellinghelli, G. Pintus, E.F. Trogu, G. Zonnedda, H.H. Wang and J. M. Williams, Inorg. ChintActa, 1998,273,175.
10. A possible correlation between the C=C bond order with the charge on the ligand would imply neglecting the charge on the metal. In the most widely accepted model for metal bis(dithiolene) complexes (Z.S. Herman, R.F. Kirchner, G.H. Loew, U.T. Mueller-Westerhoff, A. Nazzal and M. C. Zerner, Inorg. Chem., 1982, 21, 46) thé metal atom is believed to remain in a formal oxidation state +2 with a d configuration, these complexes being thus depicted as a 14 -electron system with 5 rc electrons at each ligand and 4 at the nickel. In the most recent theoretical study using density functional calculations (see réf. 15 below) it is stated that "the natural population analysis confirms that the metal M2+ does accept electrons from the ligands but to a lesser extent than expected". Therefore, the M2t-based simple and chemically intuitive model seems still appropriate in the present case for a qualitative discussion.
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17. P. Deplano, A. lenco, C. Mealli, M.L. Mercuri, G. Pintus and E.F. Trogu, results to be published.
18. C.W. Schläpfer and K. Nakamoto, Inorg. Chem., 1975,14, 1338.
19. The assignment of the C=C vibration in Pr'jtimdt complexes is less unequivocal than in dmit and mnt complexes. Indeed, it does not appear as a strong band in the Raman spectrum and should likely fall in the IR region (1400-1260 cm"') where other bands may appear and other vibrations are expected (mainly the vibrations related to CN modes and also the CH bending of the side groups). The observed trend of a group of three strong bands in this range for [NifPHjtimdOj)] (1362, 1332-1306, 1272 cnT1), [Ni(Pr'2timdt)(dmit)] (1383, 1341-1338, 1257 cm"1), [Ni(Pr'2timdt)(mnt)] (1385, 1345-1305, 1273 cm-'), [NKPr'jtimdOj)]- (1371, 1309, 1260 cnT1), [Ni(Pr'2timdt)(dmit)]- (1375, 1315, 1283 cm'1) and [NitPr'jtimdtXmnt)]- (1382, 1318-1303, 1292 cnT1) cannot straightforwardly be accounted for. It should be noted that the lowest unfilled molecular orbital (LUMO) in the symmetrical neutral derivative is a n orbital whereas the O=C bond regions are bonding. Thus, if the v(C=C) vibration could unambiguously be identified, a shift to higher frequencies may be expected since the population of the Orbitals where the C=C bond regions are bonding increases. Moreover, a coupling of the cited vibrations cannot be excluded and this might explain the difficulty found in the assignment of the corresponding bands.
20. G. Steimecke, H.J. Sieler, R. Kirmse and E. Hoyer, Phosphorus, Sulfur Silicon Relat. Etem., 1979,7,49.
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22. E. Billig, R. Williams, I. Bernai, J.H. Waters and H.B. Gray, Inorg. Chem., 1964,3,663.