Transition metal-spirobenzopyran complex, a production process therefor and a photochromic material comprising the complex

A transition metal-spirobenzopyran complex of the general formula ##STR11## wherein R.sup.1 means an alkyl group of 1 to 20 carbon atoms or an aralkyl group. R.sup.2, R.sup.3, R.sup.4, and R.sup.5 may be the same or different and each means a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an aryl group, an aralkyl group, an alkoxy group of 1 to 5 carbon atoms, a halogen atom, a cyano group or a nitro group. R.sup.6 and R.sup.7 may be the same or different and each means a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an aryl group, an aralkyl group, a halogen atom, a cyano group or a nitro group. R.sup.8 means a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group or 1 to 5 carbon atoms, a chloromethyl group, a methacryloxymethyl group or a vinyl group. Y means a oxygen atom or a sulfur atom. M means a chromium atom, a molybdenum atom or a tungsten atom.