Combine the raspberry vinegar, mustard, soy sauce, honey, basil, thyme and pepper in a large zip top bag, add the chicken and marinate for 15 minutes. Preheat grill to medium-high, remove the chicken breasts from the marinade (reserve the marinade) place the chicken on the grill and cook for 4 - 5 minutes per side. The chicken is done when the flesh looks opaque and the chicken registers at 165 degrees. While the chicken is cooking, pour the marinade into a small saucepan and boil until reduced by half. Remove the chicken from the grill, serve with the reduced sauce.