NOVELTY - Use of alpha -effective compound (I), and an isoxazolidine compound (II), as an electron donor group in light-driven systems for charge separation, is claimed.    USE - (I)-(III) are useful e.g. to extract solar energy, preferably in photovoltaic cells; as an electron donor group in light-driven systems for charge separation, fluorescent indicators for protonic acid, e.g. sulfuric acid, pigment for e.g. watercolors; and in titanium dioxide solar cells, and data storage, preferably compact disc and DVD-plates. (III) and (IV) is useful e.g. as pigment for electrophotography e.g. Xerox process, for mass coloring of polymers e.g. polyvinylchloride, and natural materials e.g. papers and wood, security marking purposes of e.g. checks and documents, frequency conversion of light, e.g. short wavelength light to long wavelength light, decorative purpose; and as fluorescence dye in scintillators, and active substance in non-linear opticals (all claimed).    ADVANTAGE - (I)-(III) exhibit high fluorescence quantum yield, long-term stability and chemical resistance.    DETAILED DESCRIPTION - Use of alpha -effective compound of formula (X(R1)(R3)-Y1(R2)(R3)) (I), and isoxazolidine compound of formula (II), as an electron donor group in light-driven systems for charge separation, is claimed.    X, Y1 = elements with free, non-binding electron pairs, preferably element from II or III group, N, O, F, S or Cl, preferably elements from II group, N or O; and    R1-R5 = H, linear 1-37C-alkyl, in which 1-10 CH2 units are optionally substituted by carbonyl, O, S, Se, Te, cis or trans-CH = CH-, and one CH unit is optionally substituted by N, acetylenic C?=C-groups, 1,2-, 1,3- or 1,4-substituted phenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-disubstituted pyridine, 2,3-, 2,4-, 2,5- or 3,4-disubstituted thiophene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6- or 2,7-disubstituted napthalene, in which 1-2 CH-groups are optionally substituted by N, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 1,9-, 1,10-, 2,3-, 2,6-, 2,7-, 2,9-, 2,10- or 9,10-disubstituted anthracene in which one or two CH groups are optionally substituted by N, where 2-12 single H atoms of the CH2-groups are optionally substituted by halo, or CN or a linear 2-18C-alkyl, in which 1-6 CH2-units are optionally substituted by carbonyl, O, S, Se, Te, cis or trans-CH=CH-groups, in which one CH unit is optionally substituted by N, acetylenic C?=C-groups, 1,2-, 1,3- or 1,4-substituted phenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3.4- or 3,5-disubstituted pyridine, 2,3-, 2,4-, 2,5- or 3,4-disubstituted thiophene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6- or 2,7-disubstituted napthalene in which one or two carbon atoms are optionally substituted by N, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 1,9-, 1,10-, 2,3-, 2,6-, 2,7-, 2,9-, 2,10- or 9,10-disubstituted anthracene, in which one or two carbon atoms are optionally substituted by N, where 2-12 single H atoms of the CH2-group of the alkyl residue is optionally substituted by F, Cl, Br, or CN, or linear 2-18C-alkyl, in which 1-6 CH2 units are optionally substituted by carbonyl, O, S, Se, Te, cis or trans-CH=CH-, in which a CH unit is optionally substituted by N, acetylenic C=C-groups 1,2-, 1,3- or 1,4-substituted phenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-disubstituted pyridine, 2,3-, 2,4-, 2,5- or 3,4-disubstituted thiophene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6- or 2,7-disubstituted napthalene, in which one or two carbon atoms are optionally substituted by N, or 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 1,9-, 1,10-, 2,3-, 2,6-, 2,7-, 2,9-, 2,10- or 9,10-disubstituted anthracene, in which one or two carbon atoms are optionally substituted by N.    Where instead of substituents, the free valency of the methine group and/or quaternary C-atom are pair-wise connected to form rings, e.g. cyclohexane ring, and the residues of R1-R9 are optionally substituted by F, Cl, Br or I. INDEPENDENT CLAIMS are included for:    (1) a perylene bisimide-dyaden compound of formula (III);    (2) a perylenetetracarboxylic acid bisimide-nitrone compound of formula (IV);    (3) the preparation of (III); and    (4) the preparation of (IV) comprising reacting perylenebisimide-aldehyde and hydroxylamine derivative, which is N-methyl hydroxylamine or N-phenyl hydroxylamine.    R6-R10 = R1; and    X = 1-12 CH2 units, which is optionally substituted by carbonyl, O, S, Se, Te, cis or trans-CH=CH-groups, in which one CH unit is optionally substituted by N, acetylenic C?=C-groups, 1,2-, 1,3- or 1,4-substituted phenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-disubstituted pyridine, 2,3-, 2,4-, 2,5- or 3,4-disubstituted thiophene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6- or 2,7-disubstituted napthalene, in which 1-2 CH groups are optionally substituted by N, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 1,9-, 1,10-, 2,3-, 2,6-, 2,7-, 2,9-, 2,10- or 9,10-disubstituted anthracene, in which 1-2 CH groups are optionally substituted by N, where 2-12 single H atoms of CH2-group are optionally substituted by F, Cl, Br, I or CN, or a linear 2-18C-alkyl, in which 1-6 CH2-units are optionally substituted by carbonyl, O, S, Se, Te, cis or trans-CH=CH-groups, in which one CH unit is optionally substituted by N, acetylenic C=C-groups, 1,2-, 1,3- or 1,4-substituted phenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-disubstituted pyridine, 2,3-, 2,4-, 2,5- or 3,4-disubstituted thiophene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6- or 2,7-disubstituted napthalene, in which 1-2C atoms are optionally substituted by N, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 1,9-, 1,10-, 2,3-, 2,6-, 2,7-, 2,9-, 2,10- or 9,10-disubstituted anthracene, in which 1-2C atoms are optionally substituted by N, where 2-12 single H of CH2-group of alkyl residue is optionally substituted by halo, CN or linear 2-18C-alkyl, in which 1-6 CH2-units are optionally substituted by carbonyl, O, S, Se, Te, cis or trans-CH=CH-groups, in which a CH unit is optionally substituted by N, acetylenic C?=C-groups, 1,2-, 1,3- or 1,4-substituted phenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-disubstituted pyridine, 2,3-, 2,4-, 2,5- or 3,4-disubstituted thiophene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6- or 2,7-disubstituted napthalene, in which 1-2C are optionally substituted by N, or 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 1,9-, 1,10-, 2,3-, 2,6-, 2,7-, 2,9-, 2,10- or 9,10-disubstituted anthracene, in which 1-2C are optionally substituted by N.    Where instead of substituents, the free valency of the methine group and/or quaternary C-atom are pair-wise connected to form rings, e.g. cyclohexane ring, and the residues of R6-R8 are optionally substituted by F, Cl, Br or I.