{'fraction_non_alphanumeric': 0.03815028901734104, 'fraction_numerical': 0.008092485549132947, 'mean_word_length': 6.098360655737705, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Photocontrollable cation extraction with crowned oligo(spirobenzopyran)s.

The photoinduced changes of metal-ion extractability of crown ether derivatives bearing three or four spirobenzopyran moieties and their analogues were studied using 1,2-dichloroethane as the organic solvent. Under dark conditions, these compounds extracted Cu2+, Ag+, and Pb2+ with their counteranions from the aqueous phase to the organic phase. The extraction equilibrium constants of the photochromic crown ether derivatives for Cu2+ and Ag+ were determined successfully. Under UV-light irradiation conditions, the extraction of Cu2+ by crowned tris(spirobenzopyran) was enhanced, while that of Ag+ was suppressed. During the competitive metal-ion extraction of crowned oligo(spirobenzopyran)s between Cu2+ and Ag+, the metal-ion selectivity was reversed explicitly by photoirradiation.