Synthesis and properties of benzophenone-spiropyran and naphthalene-spiropyran conjugates.
We have designed and synthesized four compounds integrating luminescent and photochromic components in their molecular skeletons. Two of them combine a nitrospiropyran photochrome with either one or two naphthalene fluorophores and can be prepared in three synthetic steps. The other two consist of a nitrospiropyran photochrome and a benzophenone phosphore connected by either ether or ester linkages and can be prepared in six or five, respectively, synthetic steps. The luminescent components of these assemblies are expected to transfer energy intramolecularly to the photochromic species upon excitation and encourage their photoisomerization. Consistently, the phosphorescence of the benzophenone units and the fluorescence of the naphthalene components are effectively quenched when these species are connected covalently to a nitrospiropyran. Nonetheless, the photoisomerization of the photochrome becomes significantly less efficient after the covalent attachment to the luminescent partner. The fraction of incident radiations absorbed by either the benzophenone or the naphthalene fragment does not promote the isomerization of the photochromic appendage. Instead, irreversible transformations occur upon irradiation of the luminophore-photochrome assemblies. Thus, the covalent attachment of a benzophenone or a naphthalene to a nitrospiropyran is not a viable strategy to improve the photocoloration efficiency of the photochromic component. Even although the very same luminophores are known to sensitize intermolecularly the isomerization of nitrospiropyrans, the transition to covalent luminophore-photochrome assemblies tends to promote degradation, rather than sensitization, upon irradiation.
Tomasulo
Massimiliano
M
Center for Supramolecular Science, Department of Chemistry, University of Miami, 1301 Memorial Drive, Florida 33146-0431, USA.
Kaanumal
Sireesha L
SL
Sortino
Salvatore
S
Raymo
Françisco M
FM
D001577:Benzophenones / Q000138:chemical synthesis / Q000737:chemistry; D001578:Benzopyrans / Q000138:chemical synthesis / Q000737:chemistry; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry; D049408:Luminescent Agents / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D009281:Naphthalenes / Q000138:chemical synthesis / Q000737:chemistry; D009574:Nitro Compounds / Q000138:chemical synthesis / Q000737:chemistry
D001577:Benzophenones; D001578:Benzopyrans; D007211:Indoles; D049408:Luminescent Agents; D009281:Naphthalenes; D009574:Nitro Compounds; C088184:spiropyran; C031721:naphthalene; C047723:benzophenone