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The crystal and molecular structure of the compound azZe/M-^-oxo)(hemiporphyrazinato)iron(IV), [FeON8C26H14]", has been determined from single-crystal, three-dimensional X-ray diffraction counter data. The compound crystallizes as blue-black needles in space group P2/n with Z = 2 and unit cell dimensions (at 210 K) a = 16.090 (3) k, b = 3.975 (2) Á, c = 16.070(3) Á, and ß = 92.97 (1)°. The structure was refined by full-matrix least-squares techniques to a conventional R value of 0.045. Distorted (hemiporphyrazinato)iron units stack along the b axis and are linked into polymeric, uniformly spaced, linear

F e ( p t~)~l ( B F~)~ (ptz = 1-propyltetrazole) and the mixed crystals [Znl,Fe,(ptz)6] (BF4)2 are Fe(I1) spin-crossover compounds that exhibit light-induced excited-spin-state trapping. It is shown that (a) for x I 0.1 a single-ion treatment of both the spin equilibrium ( M H L = 510 (12) cm-', A S H L = 5.1 (2) cm-'/K at T = 100 K) and the relaxation from the excited high-spin state (.Eao = 810 (30) cm-I, A -105/s) is appropriate and (b) for 0.2 I x I 1 cooperative effects observed in the relaxation from the high-spin state are of long-range nature and therefore of elastic rather than of electronic origin.

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