Neil Diamond, who led an emotional singalong of “Sweet Caroline” at Fenway Park last weekend, is writing a song about the Boston Marathon bombings. The native New Yorker told RollingStone.com that he’s at work on some new material, and the events of last week are very much on his mind. “I’m writing now and obviously affected by this situation in Boston, so I’m writing about it just to express myself,” Diamond said, adding that the song would likely touch on other recent tragedies, including the shootings in Aurora, Colo., and Newtown, Conn. “It’s like an infestation, and I’m writing about the general situation, not just about this bombing in Boston, but what we’re going through with all of these tragedies — shootings and so on,” he says. Diamond said the plan is to get it recorded and released soon. “I spent the whole day recording it and I will spend tomorrow recording it,” he said. “With a little bit of help from the man upstairs, I’ll have it finished by the weekend.” . . . Rocker Jon Bon Jovi had the good sense to add the J. Geils Band as a “special guest” at some of Bon Jovi’s summer shows, including the July 20 gig at Gillette Stadium. Tickets are on sale now.