I just build up a image portfolio with a single HTML page where all the pictures are dynamically loaded. Everything works great so far, except for the facebook META OG:IMAGE
It's the colon. Try using single quote & double-quotes like this:
var imgSrc = $(this).find('img').attr('src'); // image stored as variable
$('meta[property="og:image"]').attr('content', imgSrc); // assigns meta property