My scope function does not run in angularjs

I am trying to make sortable table. I wrote the following View and Controller:

View:

<div class="container" ng-app>
<div ng-controller="SortableTblCtrl">
    <table class="table table-hover table-bordered span12">
        <tr>
            <th ng-repeat="metadata in metadatas" ng-click="sort('{{metadata.columnProperty}}')" style="cursor: pointer">{{metadata.columnName}} </th>
        </tr>
        <tr ng-repeat="person in persons | orderBy:predicate:reverse">
            <td>{{person.firstName}}</td>
            <td>{{person.lastName}}</td>
        </tr>
    </table>
</div>

Controller:

function SortableTblCtrl($scope) {
$scope.persons = [
    { "firstName": "firstname1", "lastName": "lastname1" },
    { "firstName": "firstname2", "lastName": "lastname2" },
    { "firstName": "firstname3", "lastName": "lastname3" }
];
$scope.predicate = "";
$scope.reverse = false;

$scope.sort = function (pred) {
    $scope.predicate = pred;
    $scope.reverse = !$scope.reverse;
};

$scope.metadatas = [
    { "columnProperty": "firstName", "columnName": "First Name" },
    { "columnProperty": "lastName", "columnName": "Last Name" }
];

}

When I click on column headers nothing happens. I found something, that is when I change ng-click="sort('{{metadata.columnProperty}}')" to ng-click="sort('firstName')" it sorts first column when I click on every column header.