The Tretyakov on Kadashevskaya

There is no permanent collection — this is an exhibition wing. See the atrium, open without a ticket, and the façades: they carry reproductions of 34 works by Russian artists.
The exhibition you came for, then the atrium and the view over Lavrushinsky from the upper level. Ten minutes on foot to the historic building.
Reference
John E. Bowlt, “Moscow & St Petersburg in Russia’s Silver Age” — the world the collection in this new wing comes out of. London: Thames & Hudson, 2008.
| Mon | closed |
| Tue–Sun today | 10:00–21:00 |
Getting there — step-free. No lift at Tretyakovskaya, but the approach from the embankment is level and there is a drop-off point. Moscow metro stations almost never have lifts to the platform, except on the Big Circle line and the MCC. A wheelchair user is better served by the surface buses, which are low-floor across the centre.
The first large exhibition of the new Kadashevskaya wing: the flower in Russian art from the icon to the 20th century.
Over 140 works from twenty collections: The Pool, The Emerald Necklace and studies almost never shown. Russian Symbolism is one of the summits at which art lifts a person beyond himself; a retrospective this full comes once in a generation.
If the Kadashevskaya wing left you wanting the rest, it is two minutes away: the permanent collection is in Lavrushinsky.