The decision, reached by the Tribune Publishing board Thursday, followed several months of negotiations with the California-based McClatchy Co. The source said potential antitrust issues in Florida, where McClatchy owns the Miami Herald and Tribune Publishing owns the nearby Sun Sentinel, ultimately derailed a deal between the two companies. Putting both those newspapers under the McClatchy corporate umbrella would have created economic synergies important to the deal but there were concerns it wouldn’t pass muster with federal regulators, multiple sources said.