Depending on what's interpreting this (probably), you won't be able to use {} within a [].

you probably want to instead do:

^([\w\s,/\-@#]|'')+$

but then I'm not sure how it'll deal with more than 2 's in a row, nor what you would want it to do.

Notice I've replaced the a-zA-Z0-9_ with \w.

More notes: I'm pretty sure parentheses don't work as parentheses inside []; they just match those characters. Therefore, you might see if your current regex will only match two close parens in a row.