Photochemical studies on the through-space S…S interaction of 2-phenylnaphtho[1,8-de][1,3]dithiin 1-oxide, 5-phenyl[1]benzothieno[4,3,2-def][1,3]benzodithiepin 4-oxide, and 2-phenyldibenzo[d,f][1,3]dithiepin 1-oxide