Jump to main content
Jump to site search
Access to RSC content Close the message box

Continue to access RSC content when you are not at your institution. Follow our step-by-step guide.


Issue 10, 1981
Previous Article Next Article

Heat capacities of β-modification phthalocyanines from 4 to 45 K. Anomalous behaviour in copper(II) and nickel(II) phthalocyanine

Abstract

Heat capacities from ca. 4 to ca. 45 K are reported for β-modification metal-free, copper(II) and nickel(II) phthalocyanine (β-H2Pc, β-CuPc and β-NiPc where Pc = C32H16N8).

β-CuPc undergoes two essentially first-order transitions implying the existence of three distinct phases, phase III stable below ca. 9 K, phase II stable from ca. 9 to ca. 12 K and phase I stable above ca. 12 K. Moreover, the sum of the two entropies of transition (for III → II and II → I) is so large (ca. R ln 4, possibly more) that it is very likely that phase I is disordered in some way. To explain the value R ln 4, we tentatively propose (i) that the disorder in phase I is positional disorder of the Cu2+ ions, to each of which there are presumed to be available four nearly equivalent potential minima in the central area of the Pc2– ligand, and (ii) that in phase III the Cu2+ ions are ordered under the influence of their mutual interaction.

At temperatures between 4 and 8 K, the molar heat capacity of β-NiPc considerably exceeds those of β-H2Pc and β-CuPc, and the latter heat capacities, unlike the former, are proportional to T3. This suggests that the heat capacity of β-NiPc below 8 K differs from those of β-H2Pc and β-CuPc in including a substantial non-vibrational contribution.

Back to tab navigation

Article information


J. Chem. Soc., Faraday Trans. 2, 1981,77, 1757-1766
Article type
Paper

Heat capacities of β-modification phthalocyanines from 4 to 45 K. Anomalous behaviour in copper(II) and nickel(II) phthalocyanine

R. M. Clay, M. Jewess and L. A. K. Staveley, J. Chem. Soc., Faraday Trans. 2, 1981, 77, 1757
DOI: 10.1039/F29817701757

Search articles by author

Spotlight

Advertisements