Using BrCCCBr, O=C(C(=O)c1ccc(O)cc1)c1ccc(O)cc1 to produce O=C(C(=O)c1ccc(OCCCBr)cc1)c1ccc(OCCCBr)cc1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.