Did try
$terms = get_terms( 'molecules_of_the_month', $args );
if ( ! empty( $terms ) ) :
$termid = get_queried_object()->term_id;
print_r($termid);
$summaryimage = get_field('summary_preview_image', $termid);
// print_r($summaryimage);
$size = 'full'; // (thumbnail, medium, large, full or custom size)
$count = count( $terms );
but also do not get the term id . Perhaps I need to do another query on top, not sure yet…