S1 Supporting Information Tailoring Photoisomerization Pathways in Donor-Acceptor Stenhouse Adducts: The Role of the Hydroxy Group Michael M. Lerch, † Miroslav Medveď, Δ,¶ Andrea Lapini, ∥ ,§ Adèle D. Laurent, ● Alessandro Iagatti, ∥ ,& Laura Bussotti, ∥ Wiktor Szymański, ‡,† Wybren Jan Buma, ▼ Paolo Foggi, ∥ ,&, ⊥ Mariangela Di Donato, *, ∥ ,&, Ben L. Feringa *,† † Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands ‡ Department of Radiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ, Groningen, The Netherlands ∥ LENS (European Laboratory for Non Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino, Italy & INO (Istituto Nazionale di Ottica), Largo Fermi 6, 50125 Firenze, Italy § Dipartimento di Chimica “Ugo Schiff”, Università di Firenze, via della Lastruccia 13, 50019 Sesto Fiorentino, Italy ⊥ Dipartimento di Chimica, Università di Perugia, via Elce di Sotto 8, 06100 Perugia, Italy Δ Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University in Olomouc, 17. listopadu 1192/12, CZ-771 46 Olomouc, Czech Republic ¶ Department of Chemistry, Faculty of Natural Sciences, Matej Bel University, Tajovského 40, SK-97400 Banská Bystrica, Slovak Republic ● CEISAM, UMR CNRS 6230, BP 92208, 2 Rue de la Houssinière, 44322 Nantes, Cedex 3, France ▼ Van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands Corresponding Author: *didonato@lens.unifi.it *b.l.feringa@rug.nl