Preheat grill over medium high heat. Season chicken breasts with salt and pepper to taste. Cook on grill until cooked through and no longer pink.
In a small bowl, combine tomatoes, garlic, olive oil, basil, salt and pepper. Place in refrigerator to allow for flavors to meld together.
To make balsamic glaze: Place vinegar in a small sauce pan and heat over medium high heat until a gentle boil. Reduce heat to low and simmer until vinegar begins to thicken (about 15 minutes).
Once chicken and glaze are complete, spoon the tomato/basil mixture over the grilled chicken and drizzle balsamic glaze over top.