Realizing chromophores that simultaneously possess substantial near-infrared (NIR) absorptivity and long-lived, high-yield triplet excited states is vital for many optoelectronic applications, such as optical power limiting and triplet–triplet annihilation photon upconversion (TTA-UC). However, the energy gap law ensures such chromophores are rare, and molecular engineering of absorbers having such properties has proven challenging. Here, we present a versatile methodology to tackle this design issue by exploiting the ethyne-bridged (polypyridyl)metal(II) (M; M= Ru, Os)-(porphinato)metal(II) (PM′; M′= Zn, Pt, Pd) molecular architecture (M-(PM′)n-M), wherein high-oscillator-strength NIR absorptivity up to 850 nm, near-unity intersystem crossing (ISC) quantum yields (ΦISC), and triplet excited-state (T1) lifetimes on the microseconds time scale are simultaneously realized. By varying the extent to which the atomic coefficients of heavy metal d orbitals contribute to the one-electron excitation configurations describing the initially prepared singlet and triplet excited-state wave functions, we (i) show that the relative magnitudes of fluorescence (k0F), S1→ S0nonradiative decay (knr), S1→ T1ISC (kISC), and T1→ S0relaxation (kT1→S0) rate constants can be finely tuned in M-(PM′)n-Mcompounds and (ii) demonstrate designs in which the kISCmagnitude dominates singlet manifold relaxation dynamics but does not give rise to T1→ S0conversion dynamics that short-circuit a microseconds time scale triplet lifetime. Notably, the NIR spectral domain absorptivities of M-(PM′)n-Mchromophores far exceed those of classic coordination complexes and organic materials possessing similarly high yields of triplet-state formation: in contrast to these benchmark materials, this work demonstrates that these M-(PM′)n-Msystems realize near unit ΦISCat extraordinarily modest S1-T1energy gaps (∼0.25 eV). This study underscores the photophysical diversity of the M-(PM′)n-Mplatform and presents a new library of long-wavelength absorbers that efficiently populate long-lived T1states.